Author name: Prasanna

Haryana State Board HBSE 8th Class Science Solutions Chapter 15 Some Natural Phenomena Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 15 Some Natural Phenomena

HBSE 8th Class Science Some Natural Phenomena Textbook Questions and Answers

Question 1.
Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth.
Answer:
(b) A copper rod

Question 2.
When a glass rod is rubbed with a piece of silk cloth the rod
(a) and the cloth both acquire positive charge.
(b) becomes positively charged while the cloth has a negative charge.
(c) and the cloth both acquire negative charge.
(d) becomes negatively charged while the cloth has a positive charge.
Answer:
(b) becomes positively charged while the cloth has a negative charge.

Question 3.
Write T against true and F against false in the following statements:
(а) Like charges attract each other. (T/F)
(b) A charged glass rod attract a charged plastic straw. (T/F)
(c) Lightning conductor cannot protect a building from lightning. (T/F)
(d) Earthquakes can be predicted in advance. (T/F)
Answer:
(a) False
(b) True
(c) False
(d) False

Question 4.
Sometime, a crackling sound is heard while taking off sweater during winters. Explain.
Answer:
This occurs due to electric discharge between sweater and body. Some energy is always released with electric discharge, which in this case is released in form of a cracking sound.

Question 5.
Explain why a charged body loses its charge if we touch it with our hand.
Answer:
When we touch a charged body, it loses its charge, due to process of earthing. Our body is good conductor of electricity and transfers the charges to the earth.

Question 6.
Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Answer:
Destructive energy of an earthquake is measured in Ricther Scale. Yes, it will be recorded in this scale. Earthquake with megnitude of 3 on Richter Scale is not much destructive.

Question 7.
Suggest three measures to protect ourselves from lightning.
Answer:
Three measure to stay protected from lightning are:

• Stay indore or under covered area.
• Don’t take bath during lightning.
• We should not use T.V. or phone during lighning.

Question 8.
Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon?
Answer:
A charged balloon is atracted by another charged balloon because both carry same charge like charge always repel each other. While the uncharged balloon is attracted by charged balloon due to unlike charged.

Question 9.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Answer:
An electroscope can be used to detect if a body is charged or not. When the metal strips repel each other proves that the body is charged as repulsion is the sure test to detect if a body carries charge or not.

Question 10.
List three states in India where earthquakes are more likely to strike.
Answer:
Kashmir, Punjab and Gujarat are more prone to earthquake.

Question 11.
Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?
Answer:
We will take following precautions :

• We will try to move to an open space.
• If we are driving, we will slow down the vehicle and move slowly away from that area.
• We will not take shelter under trees or buildings.

Question 12.
The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.
Answer:
No, we will not take an umbrella, as this will increase the risk of lighting because wide objects are more prone to lightning strike.

Extended Learning – Activities and Projects

Question 1.
Open a water tap. Adjust the flow so that it forms a thin stream. Charge a refill. Bring it near the water stream. Observe what happens. Write a short report on the activity.
Answer:
For self attempt.

Question 2.
Make your own charge detector. Take a paper strip roughly 10 cm x 3 cm. Give it a shape as shown in Fig. 15.15. Balance it On a needle. Bring a charged body near it. Observe what happens. Write a brief report, explaining its working.
Answer:
For self attempt.

Question 3.
This activity should be performed at night. Go to a room where there is a fluorescent tube light. Charge a balloon. Switch off the tube light so that the room is completely dark. Bring the charged balloon near the tubelight. You should see a faint glow. Move the balloon along the length of the tube and observe how glow changes.
Caution: Do not touch the metal parts of the tube or the wires connecting the tube with the mains.
Answer:
For self Attempt.

Question 4.
Find out if there is an organisation in your area which provides relief to those suffering from natural disaster. Enquire about the type of help they render to the victims of earthquakes. Prepare a brief report on the problems of the earthquake victims.
For more information on these topics, visit:
→ science.howstuffworks.com/lightning.htm
→ science.howstuffworks.com/ earthquake .htm
→ www enchantedlearning.com/subjects/ astronomy/planets/ earth/continents.shtml
Answer:
For self attempt.

HBSE 7th Class Science Some Natural Phenomena Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Name any three natural phenomena.
Answer:
Earthquakes, cyclones, lightning.

Question 2.
According to ancient Greeks who invented thunderbolts?
Answer:
Goddess of Wisdom Minerva.

Question 3.
What are the sparks seen in sky during thunderstorms?
Answer:
Lightning.

Question 4.
Which resin did Greeks knew, produced sparks on rubbing continuously?
Answer:
Amber.

Question 5.
What happens when we rub a plastic scale with our hair?
Answer:
It gets charged.

Question 6.
What happens when charged plastic scale is brought close to bits of paper?
Answer:
Papers get attracted towared scale.

Question 7.
What happens when we rub an inflated balloon and let it free near a wall?
Answer:
Balloon gets attached to the wall.

Question 8.
How many types of charges are gained by rubbing objects?
Answer:
Two.

Question 9.
Name the charges bodies acquire on rubbing.
Answer:
Positive charge and negative charge.

Question 10.
What happens when similar charged bodies are brought close?
Answer:
They repel each other.

Question 11.
What happens when two different charged bodies are brought close?
Answer:
They attract each other.

Question 12.
What will happen when a charged glass rod is brought close to a charged straw?
Answer:
They will attract each other.

Question 13.
What will happen when a charged pen refil is brought close to a charged balloon?
Answer:
They attract each other.

Question 14.
Which charge is conventionally called a positive charge?
Answer:
Charge on a charged glass rod.

Question 15.
A charged glass rod attracts a charged straw. What is the charge on the charged straw?
Answer:
Negative charge.

Question 16.
What is the electric charge generated by rubbing called?
Answer:
Static electricity.

Question 17.
What is the static electricity?
Answer:
Charges which are produced by rubbing and are not movable are called static electricity.

Question 18.
How is electric charges different from static charges?
Answer:
Electric charges can flow but static charges cannot move.

Question 19.
What is used to transfer electrical charges from one body to another?
Answer:
Metallic conductors.

Question 20.
What is the transfer of charges from one body to earth is called?
Answer:
Earthing.

Question 21.
What provision is made in buildings to prevent electrocution?
Answer:
Earthing of wires is done.

Question 22.
How a huge energy is produced during thunderstorm?
Answer:
By repulsion of negative charges from clouds and positive charges from ground.

Question 23.
What is the process of meeting of negative charges from clouds with positive charges from ground to release huge energy called?
Answer:
Electric discharge.

Question 24.
Which place is safe during thunderstorms and lightning?
Answer:
Covered vehicles and buildings.

Question 25.
What should be considered as alert signs to get a safe place during thunderstroms?
Answer:
Hearing thunder without lightning.

Question 26.
Is sitting on a motor-cycle safe during lightning?
Answer:
No.

Question 27.
Where should one take shelter in open during lightning?
Answer:
Under small trees.

Question 28.
Is it safe to use wired phones during lightning?
Answer:
No.

Question 29.
Can a lightning victim electrocute another person?
Answer:
No.

Question 30.
What harms can lightning cause in a lightning victim?
Answer:
Loss of memory, loss of hearing or sight, broken bones etc.

Question 31.
What is the device used to save multistoryed buildings from lightning.
Answer:
Lightning rod.

Question 32.
Where is the lightning rod attached to protect the building from lightning?
Answer:
On the top of the building.

Question 33.
One end of the lightning rod is left loose in the air, where is the other end fixed or attached?
Answer:
Other end of the rod is attached to the ground.

Question 34.
Which fish can give electrical shock?
Answer:
Electrical eel.

Question 35.
What is the capacity of producing electric current in an electrical eel?
Answer:
650 volts.

Short Answer Type Questions

Question 1.
How can charging take place by rubbing?
Answer:
When a plastic comb is rubbed with hair it starts attracting small pieces of paper. Similarly, when two straws are rubbed with polythene and are brought close they repel each Other. Rubbing charges the comb and straws by loading charges on comb and straws, The polythene and hair against which straws and combs are charged also get charged.

Question 2.
How many types of charges do things acquire on rubbing?
Answer:
Charges acquired by objects are of two types named positive charge and negative charge. Charge acquired by a glass rubbed with silk is called positive charge and the charge acquired by the silk is called the negative charge.

Question 3.
How are negative and positive charges related to each other?
Answer:
Positive charges repel each other and negative charges repel each other. In other words similar charges repel each other. On the other hand negative charge is attracted by positive charges or in simple words opposite charges attract each other.

Question 4.
What is static electricity? How is it different from electric current?
Answer:
The electrical charges acquired by bodies on rubbing are called static electricity. These charges are called static because, they cannot move. This is the difference static electricity and electrical current has. Electrical current can move or flow but static electricity cannot move or flow.

Question 5.
What is electrical discharge?
Answer:
Transfer of charges from a body is called electrical discharge. If we touch a charged object, the charge gets transferred to the earth through our body. We say that the object is discharged. This is also called earthing. Electrical discharge can take place between any two conducting bodies.

Question 6.
How electrical discharge takes place in clouds?
Answer:
During thunderstorms the negative charges get accumulated near the clouds and positive charges accumulate near ground. When these negative and positive charges meet, electrical discharge takes place between clouds and grounds. It produces huge amount of energy which is released as lightning and thunder.

Question 7.
How do clouds get charged during thunderstorms?
Answer:
During thunderstorm there is a vigorous movement of air current in upward and downward direction i.e. in opposite direction. This is similar to rubbing of objects, this vigorous movements of water droplets in clouds cause charging of the clouds.

Question 8.
How does lightning strike during thunderstroms?
Answer:
During thunderstorms, the opposite charged clouds and ground come in contact and electrical discharged takes place between clouds and ground and huge energy is released as lightning. This is called lightning strike. Electrical discharge can take place between clouds and ground, clouds and human body, clouds and building etc.

Question 9.
How can we protect ourselves from lightning during thunderstorm when we are out of our home?
Answer:
Following precautions should be used when we are out during thunderstorm:

• We should not stay in open vehicles or places.
• Should not carry unbrella.
• Should not take shelter under tall trees or under poles etc.
• If shelter has to be taken, then it should be taken under smaller trees.

Question 10.
What precautions should we take to secure ourselves from lightning stroke during thunderstorm when we are in our homes?
Answer:
Following precautions should be taken while in house :

• We should not use wired phone.
• Electrical appliances should be plugged off.
• Should not bathe in running water.

Question 11.
Why is it advised to take shelter under smaller trees while in open during thunderstorms?
Answer:
During thunderstorms, we should take shelter under smaller trees because electrical discharge can easily take place with tall trees, so they are easy targets of lightning. While smaller trees are not in reach of lightning often.

Question 12.
How does a lightning rod protect a building from lightning?
Answer:
Lightning rods are installed on the top of the buildings. One end of the rod is left in open and the other one is connected to the earth.When lightning strikes the building, the charges are directly transferred to earth by the rod, this is called earthing. Earthing thus saves the buildings from lightning strike.

Question 13.
Why the Electric Eel is so called?
Answer:
Eel found in South America emits electric discharge from its body. It can produce electric current of 650 volts. It emits discharge to attack its enemies, to give shock to the prey. It can also give shock to human beings too. As these Eels produce electric discharge, they are called electric Eels.

Question 14.
What is an earthquake? How is it measured?
Answer:
Sudden trembling and shaking of the earth is called an earthquake. Due to sudden movements in the uppermost layer of the earth, the earth starts trembling, this movement of earth is called an earthquake. The magnitude of the earthquake is measured through an instrument called seismograph and it is measured on Richter scale.

Long Answer Type Questions

Question 1.
What is static electricity? How many kinds of charges are there?
Answer:
The electrical charge produced due to rubbing of objects is called static electricity. This charge cannot move as the electric current moves. These types of charges are produced only when objects are rubbed. When we rub an inflated balloon with our hair and let it loose, it attaches to wall. This proves that balloon has been charged. Similarly when a glass rod is rubbed with silk, it gets charged.

Charges are of two types : Negative charges and positive charges. Conventionally charge acquired by a glass rod is called positive charges and the charges acquired by the silk with which glass rod is rubbed aquires a negative charge. Similarly charged bodies repel each other and oppositely charged bodies attract each ether.

Question 2.
What is earthing? How is it useful?
Answer:
Transfer of charges to earth through conducting bodies is called earthing. In buildings wiring is done to do earthing when we touch the electric current, it enters the earth through our bodies. The bodies of the living beings including humans are good conductors of electricity. So, they easily acquire charges and transfer them to the earth, if they are in contact of the earth. This is called earthing.

Earthing is very useful as it protects us from electrocution. It prevents electric shocks as it transfers current to the earth. Earthing also saves building from lightning.

Question 3.
How does lightning take place during a thunderstorm?
Answer:
Lightning during thunderstorm takes place due to a phenomenon known as electric discharge. Electric discharge means interaction between oppositely charged objects. During thunderstorms vigorous upward and downward movement of air particles take place. This causes charging of water droplets accumulate in clouds and positive charge accumulates near ground. When these positive charges and negative charges meet a huge amount of energy is released in form of thunder and lightning. This whole process is called electrical discharge.

Question 4.
How can we save ourselves from lightning?
Or
What precautionary measures should be taken to save ourselves from lightning?
Answer:
Lightning gives a warning before appearing. Huge thunder without light is a warning. We should look for a safe place. No place in open is safe.

• One should rush to take shelter in building or house.
• One should not come out of the covered vehicle if on the road.
• One should not keep sitting on open vehicles like scooters, bikes etc.
• One should not take shelter under large and tall trees as they are easy target for electrical discharge.
• One should take shelter under smaller trees while in open as they are not easy target of lightning.
• If in open and no tree or shelter nearabout, one should sit with head folded under arms and embedded between the legs. One should not lie down in open.
• We should plug out all the electrical appliances during lightning.
• We should not use wired telephones during lightning, while mobiles and cordless phones are safe.
• One should not take ones bath during lightning.

Question 5.
What is a lightning rod? How is it used?
Answer:
Lightning rod is a device which is used to save tall buildings from lightning. Tall buildings are easy target to lightning as there can be easy electrical discharge with clouds. Lightning rod is a rod having three spikes on its top and a long earthing- wire to be attached to the earth. The end with spikes is left in open and other end is attached to earth. Lightning rod is fitted on the top of the buildings. During thunderstorm, when electrical discharge takes place between clouds and the building, the lightning rod acquires the charges and transfers them to the earth through its embedded end and saves the buildings from the strike of the lightning.

Question 6.
What is an earthquake? How does it occur?
Answer:
Sudden shaking and trembling of the earth is called earthquake. It occurs due to disturbance deep inside the upper layer of the earth. Earthquake is a natural phenomenon, which can be very devastating depending upon its intensity and magnitude.

The uppermost layer of the earth is not made up of a single flat surface. It is made up of different fragments, called seismic plates. These plates are joined with each other at different points. These plates are always in a continuous motion. Sometimes due to collision of these plates or upward or downward motion of these plates earth starts shaking. This is called an earthquake. The areas falling between these plates are the areas which are the most vulnerable areas for earthquakes. These are called fault zones or in simple language danger zones.

Question 7.
What is a seismograph? How does it work?
Answer:
Seismograph is an instrument which is used to record the intensity of the earthquake. Seismograph has a long rod suspended, with a pen attached to it. A paper is placed under the pen. When an earthquake strikes, the rod starts vibrating. The pen also starts vibrating and paper starts moving under the pen recording the movement of the pen. Scientists further study the seismic waves recorded by pen and make estimates about the intensity of the earthquake. This graph also gives the idea about the energy involved in the earthquake. This idea helps in determining the destructive power of the earthquake.

Some Natural Phenomena Class 8 HBSE Notes

• Natural phenomena like lightning, earthquakes etc. always made people fearful. People had many superstitions regarding these phenomena. They related these phenomenon to wrath and pleasures of Gods.
• Greeks knew that sparks like that of lightning also Occur when amber is rubbed with fur.
• Rubbing the objects with other objects can cause charging like rubbing a plastic scale with hair can charge the scale.
• Similar charged bodies repel each other while oppositely Charged bodies attract each other.
• Charges are of two types : negative and positive.
• Charges on a charged glass rod is said to be positive and other kind of charges are called negative charges.
• Opposite charges attract each other and similar charges repel each other.
• Charges which are generated due to rubbing are called static electricity. Static electricity means where charges do not move as in electric current.
• Charges can be transferred from one body to another. Charges can be transferred from a charged body to earth and this is called earthing.
• Lightning during rain is due to release of huge energy during electric discharge.
• Lightning can be dangerous, but we can secure ourselves by using precautions.
• Lightning rods can protect tall building from lightning as tall objects are easy target for lightning.
• Earthquake is another natural phenomena which can prove disastrous.
• Earthquakes take place due to disturbance in upper crusts of the earth.

Haryana State Board HBSE 8th Class Science Solutions Chapter 16 Light Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 16 Light

HBSE 8th Class Science Light Textbook Questions and Answers

Question 1.
Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain.
Answer:
We cannot see objects in the room because it is a dark room. No light is reflected from the surfaces of the object, so we are not able to see them. But outside the room, the objects can reflect light thus enabling us to see the objects.

Question 2.
Differentiate between regular and diffused reflection. Does diffused reflection mean the failure of the laws of reflection?
Answer:
Following are the differences between a regular reflection and diffused reflection :
Regular Reflection:
(i) It takes place on a smooth surface.
(ii) It has all the reflected rays in parallel.
(iii) Reflected rays are in one direction.

Diffused Reflection:
(i) It takes place on a rough surface.
(ii) Reflected rays are not parallel.
(iii) Reflected rays are scattered in different directions.
Diffused reflection is not due to failure of laws of reflection.

Question 3.
Mention against each of the following whether regular or diffused reflection will take place when a beam of light strikes. Justify your answer in each case.
(a) Polished wooden table
(b) Chalk powder
(c) Cardboard surface
(d) Marble stone with water spread over it
(e) Mirror
(f) Piece of paper
Answer:
(a) A polished wooden table will have regular reflection because its surface is smooth.
(b) A chalk powder will ‘get the diffused reflection because chalk particles are not smooth.
(c) Cardbord surface has minute irregularities on it, so it will have a diffused reflection.
(d) Marble stone with water spread over it will have regular reflection if water is stable but if waves are formed then diffused reflection will take place.
(e) A mirror will reflect light regularly due to its smooth surface.
(f) A piece of paper will have irregular reflection due to minute irregularities on it.

Question 4.
State the laws of reflection.
Answer:
Following are the laws of reflection:
(i) Incident ray, reflected ray and normal drawn at the point of incidence to the reflecting surface always lie in the same plane.
(ii) Angle of incidence is always equal to angle of reflection.

Question 5.
Describe an activity to show that the incident rays, the reflected ray and the normal at the point of incidence lie in the same plane.
Answer:
Take a plane mirror and make it stand with help of block on a plane sheet as shown in figure. Now draw an incident line on it AB. Now see in the mirror and mark the points on the paper, where you feel the line is travelling after

getting reflected from the mirror (P₁ and P₂). Now remove the mirror and mark it as OS and Join the points to make the reflected ray. You will see that, it joins the point of incidence, proving that incident ray is the reflected ray (BC).

Question 6.
Fill in the blanks in the following:
(a) A person 1 m in front of a plane mirror seems to _________ be m away from his image.
(b) If you touch your _________ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with .
(c) The size of the pupil becomes _________ when you see in dim light.
(d) Night birds have _________ cones than rods in their eyes.
Answer:
(a) 2 m
(b) left, left
(c) increase
(d) lesser.

Choose the correct option in the Question 7-8.

Question 7.
Angle of incidence is equal to the angle of reflection:
(i) Always
(ii) Sometimes
(iii) Under special conditions
(iv) Never
Answer:
(i) Always.

Question 8.
Image formed by a plane mirror is:
(a) virtual, behind the mirror and enlarged
(b) virtual, behind the mirror and of the same size as the object
(c) teal at the surface of the mirror and enlarged
(d) real, behind the mirror and of the same size as the object.
Answer:
(b) virtual, behind the mirror and of the same size as the object.

Question 9.
Describe the construction of kaleidoscope.
Answer:
Kaleidoscope is made of three strips of plane mirrors. Three strips of plane mirrors of about 15 cm. length and 4 cm. width are taken and arranged as in a prism i.e. in a triangular form.

They are fixed to each other with thick sheet of paper and enclosed in a tube or in a circular carboard. One end of the tube is covered with a round cardboard disc having a hole in the centre. From the opposite open end some pieces of broken bangles or broken coloured glass are put inside the tube. This open end is also closed. When we see inside this tube through the hole in the circular cardboard; we see different patterns of coloured bangle inside it.

Question 10.
Draw a labeled sketch of human eye.
Answer:

Question 11.
Gurmit wanted to perform Activity 16.8 using a laser torch. Her teacher advised her not to do so. Can you explain the basis of the teacher’s advise ?
Answer:
Teacher has advised her to because laser light is harmful for eyes and can cause some permanent damage to eyes when throw directly in eyes.

Question 12.
Explain how you can take care of your eyes?
Answer:
Following precautionary measures can be taken to take care of our eyes:

• We should always wash our eyes with plane cold water atleast three times a day.
• We should not touch our eyes with dirty hands.
• We should never rub our eyes.
• We should not look at Sun directly.
• We should read book, watch T.V., read from black board from a suitable distance.
• Consult an eye specialist if have any irritation, redness in our eyes.

Question 13.
What is the angle of incidence of a ray if the incident and reflected rays is at an angle of 90° to the incident ray?
Answer:
The angle of incidence of the ray will be 45°.

Question 14.
How many images of a candle will be formed if it is placed between two parallel plane mirrors separated by 40 cm?
Answer:
Infinite images will be formed.

Question 15.
Two mirrors meet at right angles. A ray of light is incident on one at an angle of 30° as shown in the figure. Draw the reflected ray from the second mirror.

Answer:

Question 16.
Bhoojo stands at A just on the side of a plane mirror as shown in figure. Can he see himself in the mirror ? Also can he see image of objects situated at P, Q and R?

Answer:
Bhoojo can’t see himself. He can see the images of objects at P and Q.

Question 17.
(a) Find out the position of the image of an object situated at A in the plane mirror, (figure)
(b) Can Paheii at B see this image?
(c) Can Bhoojho at C see this image?
(d) When Paheii moves from B to C, where does the image of A move?

Answer:
(a) Image will be formed at ‘A’.
(b) Yes, Paheii at B can see the image.
(c) No, Boojho can’t see the image at C.
(d) The image will disappear at Paheii moves from B to C.

Extended Learning – Activities and Projects

Question 1.
Make your own mirror. Take a glass strip or glass slab. Clean it and put it on a white sheet of paper. See yourself in the glass. Next put the glass slab on a black sheet of paper. Again look into the glass. In which case do you see yourself better and why?
Answer:
For self attempt.

Question 2.
Make friends with some visually challenged students. Enquire from them how they read and write. Also find out how they are able to recognise objects, hurdles and currency notes.
Answer:
For self attempt.

Question 3.
Meet an eye specialist. Get your eye sight checked and discuss how to take care of your eyes.
Answer:
For self attempt.

Question 4.
Survery your neighbourhood. Find out how many children below the age of 12 years use spectacles. Find out from their parents what, in their view, could be the reason for the weak eyesight of’ their children.
You can read more on this topic on the following websites :
→ www.glenbrook.k 1 2.il.us/gbssci/phys/ mmedia/optics/ifpm.html
→ www.glenbrook.k 1 2 il.us/gbssci/phys/elass/ refln/u131b.html
Answer:
For self attempt.

HBSE 7th Class Science Light Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is sense of sight?
Answer:
The sense which enables us to see object around us is called sense of sight.

Question 2.
What are the sight organs in animals?
Answer:
Eyes.

Question 3.
What is a mirror?
Answer:
Smooth and shiny surface is called a mirror.

Question 4.
What is reflection?
Answer:
Throwing back the incident light by a plane surface is called reflection.

Question 5.
What kind of surfaces reflect light?
Answer:
All surfaces reflect light.

Question 6.
What is incident ray?
Answer:
Beam of light falling on reflecting surface is called incident ray.

Question 7.
What is reflecting ray?
Answer:
Beam of light reflected back by the reflecting surface is called reflected ray.

Question 8.
What is angle of incidence?
Answer:
Angle formed between the incident ray and normal is called angle of incident.

Question 9.
What is angle of reflection?
Answer:
Angle formed between the reflecting ray and normal is called angle of reflection.

Question 19.
State second law of reflection.
Answer:
Angle of incidence and angle of reflection are always same.

Question 11.
What kind of image is formed by a plane mirror?
Answer:
Virtual and erect image.

Question 12.
Where is the image formed by the mirror?
Answer:
Behind the mirror.

Question 13.
What is the size of the image formed?
Answer:
Same as that on the object infront of the mirror.

Question 14.
At what distance is the image formed behind the plane mirror?
Answer:
At the same distance, as is the object infront of the mirror.

Question 15.
What is the phenomenon called where left side appears to be right and vice- versa in a plane mirror?
Answer:
Lateral inversion.

Question 16.
Which surface shows regular reflection?
Answer:
Smooth surface.

Question 17.
Which surface shews diffused reflection?
Answer:
Rough surface.

Question 18.
What kind of reflection will take place from a polished leather shoes top?
Answer:
Regular reflection.

Question 19.
What kind of reflection will take place from the cover of your note-hook?
Answer:
Diffused reflection.

Question 20.
In what kind of reflection does reflected rays go parallelled to each other?
Answer:
Regular reflection.

Question 21.
In what kind of reflection, reflected rays move scattered?
Answer:
In diffused reflection.

Question 22.
floes Moon has its own light?
Answer:
No.

Question 23.
How does moon shine?
Answer:
It reflected light emitted by the Sun.

Question 24.
Name some objects which have light of their own.
Answer:
Sun, fire, flame of candle etc.

Question 25.
What are objects called, which have light of their own?
Answer:
Luminous objects.

Question 26.
How many mirror strips are used to make a Kaleidoscope?
Answer:
Three.

Question 27.
Is white light a pure white light?
Answer:
No.

Question 28.
How many colours constitute a white beam?
Answer:
Seven.

Question 29.
What is the splitting of white light into its constituent colours called?
Answer:
Dispersion.

Question 30.
What is the shape of human eye?
Answer:
It is roughly spherical in shape.

Short Answer Type Questions

Question 1.
What is reflection of light?
Answer:
When a beam of light falls on a surface, it is thrown back by the surface in a different direction in the same medium. This is called reflection of light. Every surface can reflect. The falling beam of light is called incident ray and beam bouncing back is called the reflected ray.

Question 2.
How do we see various objects?
Answer:
We see various objects due to reflection. As we know all surfaces reflect light, when light falls on any object, it reflects the light. The reflected light reaches our eyes and we are enabled to see the objects.

Question 3.
Write the laws of reflection?
Answer:
There are two laws of reflection :
(i) The ray of incidence, ray of reflection and normal drawn at the point of incidence to the reflecting surface lie in the same plane.

(ii) The angle of reflection and angle of incidence are always equal.

Question 4.
What do you mean by following.
(i) Incident ray
(ii) Reflected ray
Answer:
Incident ray : The light ray that strikes any surface is called incident ray.
Reflected ray : The light ray which is thrown away from the surface after reflection in a different direction, is called reflected ray.

Question 5.
What do you mean by angle of incidence and angle of reflection?
Answer:
The angle formed between the incident ray and the normal is called the angle of incidence. The angle of reflection is the angle formed between the reflected ray and the normal. Both these angles are always equal in size.

Question 6.
What is a mirror? What kind of image is formed in a mirror?
Answer:
Any smooth and shining surface can act as mirror. Mirror is a smooth surface which is polished from its back and can form the image of the object which is placed in front of it. The image formed by a mirror is a virtual and erect image and is of same size as that of the object infront of it.

Question 7.
What is dispersion of light?
Answer:
A beam of white light consists of seven colours. When a beam of white light passes through a prism, it splits into its seven constituent colours. The splitting of white light into its seven constituent colours is called dispersion of light.

Question 8.
How many kind of nerve endings are there in our eyes?
Answer:
There are two types of nerve endings in our eyes. The first type of nerve endings are called cones. Cones are sensitive to bright light and other type of nerve endings are called rods. Rods are sensitive to dim light cones are also sensitive to colours.

Question 9.
How do eye muscle adjust themselves to see the near and distant objects?
Or
What is called the accomodation of eyes?
Answer:
The muscles of the eye contract in order to see near objects. When they contract the lens becomes thicker. When the eye has to see a distant object the muscles expand or relax. This makes the lens thinner. This is called accommodation.

Question 10.
What is the cause of dispersion?
Answer:
Different colours of light bend by different angles of refraction. When light enters the glass prism or a drop of water, different colours bend at different angles and become separated to show phenomenon of dispersion.

Question 11.
How do ciliary muscles affect the functioning of eye?
Answer:
Ciliary muscles can contract and relax. Because of this they can change the thickness of eye lens which also changes its focal length. With change in focal length eye lens can make image of near by objects and also far away objects. So power of accommodation of eye is due to the function of the ciliary muscle.

Question 12.
What is a yellow spot in eyes?
Answer:
Yellow spot or macula is a small area, facing the eye lens. It has high concentration of light sensitive nerve endings or cones. The rest of the retina has lesser cones and more number of cells called rods. It is the spot where brightest vision is formed and colour version is formed.

Question 13.
What is the blind spot?
Answer:
It is a region below the yellow spot, where no light sensitive nerve endings are present. It is an area of no vision.

Question 14.
What is Myopia or short sightedness?
Answer:
This is a type of eye defect, in which person can see nearer objects clearly but cannot see the far off objects. This defect is due to thickness of eye lens. Ciliary muscles do not relax enough to make lens thin enough to see distant objects.

Question 15.
What is Hypermetropia or long sightedness?
Answer:
This is a type of an eye defect, in which the person can see far off objects clearly, but cannot see the nearer objects. This defect is due to thinness of the eye lens. The ciliary muscle do not contract enough to make the lens see nearer objects.

Question 16.
What is cataract? How can it be corrected?
Answer:
During old age, the eye sight becomes blurred. It happens because the lens of the eye becomes opaque and milky. When the vision becomes cloudy the person is said to have cataract. It is possible to treat this temporary loss of vision by removing the opaque lens and, a new artificial lens is inserted by minor and simpe operation.

Question 17.
Write any three safety measures to protect our eyes.
Answer:

• We should not rub our eyes.
• We should wash our eyes many times a day.
• We should not look at sun or other powerful lights directly.

Question 18.
What is Braille system?
Answer:
Braille is based on code of one to six dots which are raised. Each dot has a position. These dots make up letters of alphabet, number and all other things done in print. Any language can be read through the codes of the braille by touching the dots.

Long Answer Type Questions

Question 1.
What is reflection of light? State laws of reflection.
Answer:
Reflection of light is throwing back of light by any object. When a beam of light falls on some surface, the surface throws that beam away in different direction. This is called reflection of light. Following are the laws of reflection:

(a) When a ray of light falls on a reflecting surface, it is reflected in such a way that the angle of incidence is equal to the angle of reflection i.e. ∠i = ∠r.

(b) The incident ray, the normal and the reflected ray, all lie in the same plane.

Question 2.
What are the characteristics of image formed with a plane mirror?
Answer:
Plane mirror is a shiny, polished surface. When any object is placed in front of the mirror, an image is formed. Following are the characteristics of the image formed by a plane mirror:

• Image formed on a plane mirror cannot be taken on a screen, such image is called a virtual image.
• Image formed on a plane mirror is erect.
• It is laterally inverted i.e. left hand of the object appears as the right hand.
• Image formed is as far behind as the object is in front of it.

Question 3.
What are the uses of a plane mirror?
Answer:

• We use a plane mirror to see our reflections in it, at our homes.
• Plane mirrors are used to reflect light on a particular object.
• Plane mirrors are used for signalling by scouts and army.
• They are used to form multiple images in show windows.
• Plane mirror is used to reflect sun rays in appliances like solar cooker etc.
• Toys like Kaleidoscope are made on the concept of multiple reflection. Navy use periscopes based on concept of multiple reflection for spying in sea.

Question 4.
Describe how does human eye work?
Answer:
The light reflected by objects enter our eyes through cornea. That is why cornea is called window to the world. Lens focuses the image of the object on the retina. Retina converts these optical images into optical pulses. These optical pulses are then sent to brain through optical nerves. The amount of light entering the eye through cornea is controlled by Iris. It expands when light is bright and thus enables the pupil to enter controlled amount of light to enter the eye. In dark it contracts and increases the size of pupil to allow more light to enter the eye.

The retina forms a small and inverted image of the object. The brain interprets it and forms the erect and correct sized image.

Question 5.
Write various measures to save our eyes.
Answer:
Eyes are a precious gift of God. We should take proper care of our eyes and protect them from injury. Following measures should be taken for healthy eyes :

• We should wash our eyes with cold water everyday and wipe them with clean and soft cloth.
• We should never rub our eyes. If some particle enters our eyes, we should wash our eyes with cold water.
• We should always read in proper light.
• In case of any injury or other problems related to eyes, we should avoid self medication and immediately consult an eye specialist.

Question 6.
What is blindness? How many types of blindness do we know about?
Answer:
A person is said to be blind or visually impaired when he or she is imable to see. Blindness is of two types:
Curable Blindness : When cornea becomes opaque or the lens becomes opaque the sight of the person becomes decreased. This is called a temporary or curable blindness. In this case the person is operated upon and sight is resorted. An artificial lens is inserted in place of opaque lens and the opaque cornea is replaced with a healthy donated cornea.

Permanent Blindness : In this type of blindness image formed by cornea is not transferred to brain and this type of blindness cannot be cured.

Pollution of Air and Water Class 8 HBSE Notes

• We see all the things around us only due to sense of sight.
• Eyes are our organs of sight, which enables us to see objects around us.
• It is the light which enables our eyes to see the objects. Without light our eyes cannot sense anything.
• Any polished or shiny surface acts as a mirror. It can change the direction of light.
• Light is reflected from all the surfaces.
• When a beam of light falls on a surface, it throws back the light to same medium. This phenomenon is called reflection of light.
• The beam of light falling on the plane surface is called the incident ray.
• The beam of light thrown back by the reflecting surface is called the reflected ray.
• The line drawn between the point where the incident ray and reflected ray meet is called the normal.
• The angle between the normal and the incident ray is called angle of incidence.
• The angle between the normal and the reflected ray is called the angle of reflection.
• The angle of incidence and the angle of reflection are equal.
• Incident ray, reflected ray and the normal drawn at the point of incidence to reflecting surface lie in the same plane.
• Above two points are called laws of reflection.
• Light falling on a smooth surface is reflected regularly.
• Irregular or diffused reflection takes place on rough surface.
• In mirror the right appears as left and left as right. This is called lateral inversion.
• Two mirrors inclined to each other at different angles, give multiple images.
• White light consists of seven colours called spectrum.
• Splitting of white light into its constituting seven colours is callled dispersion.
• Our eyes have different parts which perform different functions to enable us to see the objects.
• Visually challenged persons can read and write using Braille system.

Haryana State Board HBSE 8th Class Science Solutions Chapter 17 Stars and the Solar System Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 17 Stars and the Solar System

HBSE 8th Class Science Stars and the Solar System Textbook Questions and Answers

Question 1.
Which of the following is NOT a member of the solar system?
(a) An asteroid
(b) A satellite
(c) A constellation
(d) A comet
Answer:
(c) A constellation

Question 2.
Which of the following is NOT a planet of the sun?
(a) Sirius
(b) Mercury
(c) Saturn
(d) Earth
Answer:
(a) Sirius

Question 3.
Phases of the moon occur because:
(a) we can see only that part of the moon which reflects light towards us.
(b) our distance from the moon keeps changing.
(c) the shadow of the Earth covers only a part of the moon’s surface.
(d) the thickness of the moon’s atmosphere is not constant.
Answer:
(c) the shadow of the Earth covers only a part of the moon’s surface.

Question 4.
Fill in the blanks :
(a) The planet which is farthest from the Sun is __________.
(b) The planet which appears reddish in colour is __________.
(c) A group of stars that appear to form a pattern in the sky is known as a __________.
(d) A celestial body that revolves around a planet is known as __________.
(e) Shooting stars are actually not __________.
(f) Asteroids are found between the orbits of __________ and __________.
Answer:
(a) Neptune
(b) Mars
(c) constellation
(d) Satellite
(e) Meteors
(f) Mars and Jupiter.

Question 5.
Mark the following statements as true (T) or false (F) :
(а) Pole star is a member of the solar system. ( )
(b) Mercury is the smallest planet of the solar system ( )
(c) Uranus is the farthest planet in our solar system. ( )
(d) INSAT is an artificial satellite. ( )
(e) There are nine planets in our solar system. ( )
(f) Constellation Orion can be seen only with the telescope. ( )
Answer:
(a) False
(b) False
(c) False
(d) True
(c) False
(f) False

Question 6.
Match items in Column A with one or more items of Column B :

Answer:

Question 7.
In which part of the sky can you find Venus if it is visible as an evening star?
Answer:
In western sky.

Question 8.
Name the largest planet of the solar system.
Answer:
Jupiter.

Question 9.
What is a constellation? Name any two constellations.
Answer:
A group of stars in a recognizible shape is called a constillation. Orion and the Great Bear are constellations.

Question 10.
Draw sketches to show the relative positions of prominent stars in (i) Ursa Major and (ii) Orion.
Answer:

Question 11.
Name two objects other than planets which are members of the solar system.
Answer:
Meteors and Asteroids.

Question 12.
Explain how you can locate the Pole Star with the help of Ursa Major.
Answer:
Pole star is situated at the end of the Ursa Major. If a straight line starting from the last two stars is extended towards the north direction, it will lead to the Pole Star.

Question 13.
Do all the stars in the sky move? Explain.
Answer:
All the stars in the sky do not move, but they appear to move from east to west. This is actually due to rotation of earth on its axis. Earth moves from west to east. So it appears as the stars are rising from east and as the day dawns they sets in the west.

Question 14.
Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light years away from the earth?
Answer:
Stars are away from the earth millions of kilometres away. It is not convenient to express such a large distance in the units of km. So the distance of stars from the earth is expressed in time taken by light to travel in one year. Eight light years mean time taken by light to travel in eight years.

Question 15.
Boojho made the following sketch (figure) of the solar system. Is the sketch correct? If not, correct it.
Answer:
No, the sketch is incorrect. The following sketch is correct.

Extended Learning – Activities and Projects

Question 1.
If possible, visit a planetarium. There are planetariums in many cities. In a planetarium you can see the motion of the stars, constellations and planets on a large dome.
Answer:
For self attempt.

Question 2.
On a moonless night observe the sky for a few hours. Look out for a meteor, which appears as a streak of light. September-November is a good time for observing meteors.
Answer:
For self attempt.

Question 3.
Learn to identify the planets visible to the naked eye and some prominent constellations such as Great Bear (Saptarshi) and Orion. Also try to locate the Pole Star and the star Sirius.
Answer:
For self attempt.

Question 4.
Select a convenient place on the roof of your house or in some playground from where you can watch sunrise clearly. Remember that you will have to do this activity for a few months. So, choose the place carefully. On a sheet of chart paper draw the outline of the eastern horizon indicating big trees, poles, etc. Mark the outline of the sheet so that you can place it in the same position every time. After every two weeks, note the position from where the Sun rises and mark this on your chart paper (Fig.). Also note the date of your observation. Repeat this for a few months. It is advisable that you start observations in the month of November or May.

Does the Sun always rise from the same direction? Discuss your observations with you teacher, parents and elderly people in your family or in the neighbourhood.
Answer:
For self attempt.

Question 5.
Form a group of studens. Prepare a model of the solar system showing the planets, and their relative sizes. For this take a large chart paper. Make spheres representing different planets according in their relative size (Use Table). You may use newspaper, clay or plasticine to make spheres. You can cover these spheres with paper of different colours. Exhibit your model in the class.

Answer:
For self attempt.

Question 6.
Try to make a scale model of the solar system showing distances of the planets from the Sun (Use Table 17.1). Did you face any difficulty? Explain it.
Answer:
For self attempt.

Question 7.
Solve the following riddle and try to make similar riddles yourself:
My first is in VAN but not in PAN
My second is in EARTH and also in HEAVEN
My third is in ONE and not in TWO
My fourth is in BUN and also in FUN
My last is in STAR but not in RADAR
I am a planet that moves round the Sun.
You can read more on the following websites:
→ http://www.nineplanets.org
→ http://www.kidsastronomy.com
→ http://www.solarsystem.nasa.gov/planets
→ http://aa.usno.navy.mil/fazz/does/moon- phases.html
Answer:
For self attempt.

HBSE 7th Class Science Stars and the Solar System Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Name any three celestial bodies.
Answer:
Stars, Satellite, Planets.

Question 2.
Name the planets of solar system which cannot be seen by naked eye?
Answer:
Neptune and Pluto.

Question 3.
Name the force which makes planets move around the sun.
Answer:
Gravitational force.

Question 4.
Which has higher density : Earth or Sun?
Answer:
Earth.

Question 5.
Name the planet narest to earth.
Answer:
Mars is nearest to earth.

Question 6.
Write the names of any two constellation.
Answer:
Great Bear and Orion.

Question 7.
A group of stars visible in winter season look like a cluster of twinkling gems.
Answer:
Pleiades constellation.

Question 8.
In which season of the year are the constellations scorpio and orion visible in the Northern Hemisphere?
Answer:
Orion – Winters.
Scorpio – Summers.

Question 9.
Define star.
Answer:
Stars are the heavenly bodies that are extremely hot and have light of their own.

Question 10.
Name the star which is nearest to the earth.
Answer:
Alpha Centuari.

Question 11.
Write the names of two planets which are closer to the sun than the earth.
Answer:
Mercury and Venus.

Question 12.
Name the planet nearst to the sun.
Answer:
Mercury.

Question 13.
Name the planet farthest from the sun.
Answer:
Neptune.

Question 14.
Which planet of the solar system is the hotest?
Answer:
Mercury.

Question 15.
Name the planet of the solar system Which is nearer to the Sun and Venus.
Answer:
Mercury.

Question 16.
Which planet in the solar system is nearest to the earth?
Answer:
Venus.

Question 17.
Name the planet, where there is no carbon dioxide.
Answer:
Mercury.

Question 18.
Name the planets, which has no moon?
Answer:
Mercury and Venus.

Question 19.
Give any two applications of remote sensing.
Answer:
(i) Preparing waste land maps.
(ii) Survey for ground water and mineral resources.

Question 20.
A constellation having seven prominent stars, is visible during the winter. Name the constellation.
Answer:
Orion.

Question 21.
A belt of assorted debris, which failed to assemble into a planet, is located between the orbits of two planets in the solar system. Name these two planets.
Answer:
Mars and Jupiter.

Question 22.
Which planet has rings around it?
Answer:
Saturn.

Question 23.
Name largest asteroid.
Answer:
Ceres.

Question 24.
Why do meteors shine?
Answer:
On entering earth’s atmosphere, meteors become hot and bum due to friction of earths atmosphere and start to shine.

Question 25.
What are meteorites?
Answer:
Big pieces of rock material which do not bum completely in atmosphere of earth, fall on its surface. These are called meteorites.

Question 26.
How are comets formed?
Answer:
When the path of objects near the edge of solar system is disturbed to push them near to sun, comets are formed.

Question 27.
After how much time Halley’s comet is seen?
Answer:
After every 76 years.

Question 28.
Why does pole star appear to be stationary?
Answer:
Pole star lies on the axis of rotation of earth and appears stationary when viewed from any part of earth.

Question 29.
What does the colour of a star signify?
Answer:
Colour of a star signifies its temperature.

Question 30.
Define a satellite.
Answer:
A satellite is a solid heavenly small sized body revolving round a planet.

Short Answer Type Questions

Question 1.
Distinguish between stars and planets.
Answer:

Question 2.
Explain the importance of stars for the people in ancient times.
Answer:
In ancient times when there were no compass, night sky was very useful in finding the direction. As pole star remains fix in the sky in north, it indicated north direction. As the stars change their position with time, it has been possible to find the time with relative position of stars.

Question 3.
How is the pole star located in the sky? Why is it so special?
Answer:
The earth rotates on its axis from west to east, therefore, the stars appear to move in opposite direction, i.e. east to west. But pole star lies on the axis of rotation of earth which is fixed, Therefore, pole star also seems to be fixed in the sky. It is always in north direction and is very useful for finding direction.

Question 4.
Distinguish between star and shooting star.
Answer:

Question 5.
What is a meteor? Why does it last for a very short time?
Answer:
Meteors are the heavenly bodies made of rocky material which enter earth’s atmosphere. When they travel through air they become hot and burn because of friction. Due to this, these rocky pieces melt and vaporises very fast and do not last long.

Question 6.
Distinguish between natural and artificial satellites.
Answer:
Natural satellites are far away from planets. They are comparatively larger in size and are present naturally. Artificial satellites are sent from earth with specific requirements. Their distanc, size and mass are lesser than the natural satellite.

Question 7.
What is solar system? Name the planets situated between the sun and the earth?
Answer:
The solar system consists of the sun, eight planets; and their satellites and other heavenly bodies like meteors, comets and asteroids. The sun is the centre of the solar system and all the planets revolve around the sun in elliptical paths called orbits. The planets situated between the sun and the earth are Mercury and Venus.

Question 8.
What are the phases of the Moon?
Answer:
Moon has no light of its own. It reflects light of the Sun falling on it. On new moon day, moon is between the sun and the earth and no reflected light from it reaches the earth. We cannot see moon on that day. The visible moon increases every day till fifteenth day from the new moon day, the full phase of the moon is visible.

Positions of the Moon in its orbit and its corresponding phases
So, the waxing and waning of moon periodically as it revolves around the earth is called phases of moon.

Question 9.
Why moon cannot be used as a communication satellite?
Answer:
Moon is a natural satellite of the earth but it cannot be used as a communication satellite because :

• It is very far away from earth.
• Its time period 27.3 days is too large.
• It has neither equitorial orbit nor polar orbit which makes a satellite useful for different purposes.

Question 10.
What are constellations? Name some easily recognizible constellations in the sky.
Answer:
Group of stars forming a recognizible shape is called a constellation. These group of stars are identified in different shapes. Constellations do not change their shape. They also appear to move from east to west as other stars appear to. Some major constellations are Ursa Major, Ursa Minor, Orion, Cassiopeia etc. Some of them are visible during summers while some are visible during winters.

Question 11.
What are various types of motions associated with the planet earth?
Answer:
The earth has four types of motion. These are :

(i) The earth’s daily rotation on its axis.
(ii) The earth’s annual revolution around the sun.
(iii) The earth’s precession (conical motion of earth’s axis).
(iv) As a part of solar system, the earth’s motion in space along with the sun.

Question 12.
Explain the constellation Ursa Major.
Answer:
Ursa Major is one of the most famous constellation. We can see this constellation during summers. It is also called the Great Bear or the Saptarishi. There are seven prominently shining stars in this constellation which are arranged in shape of a question mark. At the tail of this constellation lies the Pole Star.

Question 13.
Describe the constellation also called the hunt.
Answer:
A well known constellation named Orion is also called the hunter. This constellation can be seen in the late evenings of winter. It has seven or eight brightly shining stars arranged in shape recognized with hunter. The brightest star in the sky Sirius is located at the extended line from the tail of this constellation.

Question 14.
What are asteroids?
Answer:
Asteroids are the small objects which revolve around the sun in a large gap between the orbits of Mars and Jupiter. These are quite large in their number and are considered as the part of our solar system. Each asteroid has its own orbit.

Question 15.
What are comets?
Answer:
Comets are the part of our solar system which revolve around the sun in highly elliptical orbits. It appears with a bright head and a long tail. The length of the tail grows in size as it approaches the sun. The tail is always directed away from sun.

Question 16.
What are various superstitions connected with appearance of comets?
Answer:
They are considered to be the messangers of destruction and disasters. They are supposed to bring wars,epidemics and flood with them. So, their appearance is considered as unauspicious.

Question 17.
List five uses of artificial satellites.
Answer:

• Weather forecasting.
• Radio and television transmission.
• Long distance communication.
• Locating mineral resources.
• Gathering information about our space.

Long Answer Type Questions

Question 1.
Explain celestial sphere.
Answer:
The large imaginary sphere on which all the heavenly bodies like stars, planets and satellites seems to lie is known as celestial sphere. Since we are on the earth, the earth appears stationary to us. When we look at the sky, the various objects in the sky like the stars and the moon appear to be moving round the earth. In other words, the celestial sphere appears to be moving from east to west round the earth. This apparent motion of the celestial sphere from east to west is actually due to the daily rotation of the earth from west to east. Since the earth rotates from west to east, the celestial sphere appears to rotate in the opposite direction, from east to west.

Question 2.
What are constellations? Explain. Name some prominent constellations with their Indian names.
Answer:
The groups of stars which seem to be arranged in the sky in beautiful patterns and recogniseable shapes are known as constellations. With each constellation, the ancient astronomers assigned the name of an object which it appears to resemble. There are 88 constellations into which the whole of the sky has been divided. In Indian astronomy, the constellations are known as Nakshatras.

Some prominent constellations with their Indian names are given below :
(i) Ursa Major or Saptarishi.
(ii) Ursa Minor or Laghu Saptarishi
(iii) Orion or Mriga or Vyadha
(iv) Tarus or Vrashba
(v) Scorpio or Vrishchika.

Question 3.
What is pole star? What is specific j about its position in the sky?
Answer:
There is only one star in the sky which appears stationary to an observer on earth. This star is named as pole star (Polaris) or Dhruvtara in India. This star appears stationary because, i it lies in the direction of the axis of the Earth about which the earth rotates. Any point on or j along the axis of a rotating body appears to be stationary. So, the pole star that lies along the direction of the axis of rotation of the earth, always sppears to be stationary.

Question 4.
What are artificial satellites? Explain their usage.
Answer:
Man made objects orbitting in outer space around the earth or any other planet are called artificial satellites of earth or that particular planet. The satellite like INSAT 3E or Kalpana Chawla I are examples of artificial satellites. Artificial satellites have many practical applications that effect our lives in many ways, i Long distance transmission of television programmes, communication through telephones and internet could be possible because of them. Artificial satellites are also used for research, defence and remote sensing. Remote sensing means collecting information from a distance. Information is collected regarding weather, agriculture, land and ocean features including movement of fish.

 Stars and the Solar System Class 8 HBSE Notes

• We can see many celestial bodies in a clear night sky.
• Stars are one of the celestial bodies which emit light of their own.
• Sun is also one of the stars which emits light and is a great source of heat. It is the closest star which is the centre of our solar system.
• Stars are many light years away from the earth and thus look very small from earth.
• Stars appear to travel from east to west.
• Pole star is the most shining star in the night sky. The pole star appears to.be stationary. It is situated near axis of rotation of earth and is thus helpful in finding direction.
• A group of stars, appearing in different shapes are called constellations. Their shapes resemble different objects and thus are named after the names of the objects.
• Other improtant parts of night sky are the planets. Planets are those celestial bodies, which revolve around sun.
• Our solar system consists of eight planets revolving around sun. It also consists of many other celestial bodies like asteroids, comets and meteors.
• Comets are the celestial bodies that revolve in highly elliptical orbits around sun.
• Bright streak of light in a night sky are commonly called shooting stars or meteors.
• A celestial body revolving around another celestial body is called a satellite.
• Artificially sent bodies in space, which revolve around earth or any other planet or a natural satellite is called an artificial satellite
• Jupiter is the largest planet while Venus is brightest planet in the night sky.
• Moon is the natural satellite of the earth. Moon appears in different phases. The phases of Moon occur because we can see only that part of the moon which reflects light towards us.

Haryana State Board HBSE 8th Class Science Solutions Chapter 18 Pollution of Air and Water Textbook Exercise Questions and Answers.

Haryana Board 8th Class Science Solutions Chapter 18 Pollution of Air and Water

HBSE 8th Class Science Pollution of Air and Water Textbook Questions and Answers

Question 1.
What are the different ways in which water gets contaminated?
Answer:
Water gets contaminated by the following ways:

• Water gets contaminated when sewage is disposed off in rivers.
• Chemicals which are harmful and poisonous are thrown in water resources by various industrial units.
• Harmful chemicals used in agricultural process gets mixed with ground water making it unfit for consumption.
• Breeding of microorganisms in water make water polluted.

Question 2.
At an individual level, how can you help reduce air pollution?
Answer:
We can plant tree to reduce the level of carbon dioxide. We can get our vehicles serviced well to reduce uncomplete consumption of fuels. We can also reduce air pollution by saying no to crackers during Diwali celebrations.

Question 3.
Clear, transparent water is always fit for drinking. Comment.
Answer:
Water which is clear and through which we can see is fit for consumption because this type of water is free from pollutants. Transparent water means no microorganisms and no dust particles.

Question 4.
You are a member of the municipal body of your town.
Make a list of measures that would help your town to ensure the supply of clean water to all its residents.
Answer:

• To get clean water in every household, it is necessary that water reaching houses should be treated water. Water is treated in sewage plants, to make it free from physical, chemical and biological impurities.
• Strict laws should be enforced on industrial units, which dispose polluted water in water resources.
• Open defecation in water resources by slum dwellers should be strictly prohibited.
• Chlorine tablets should be distributed for purification of water during rainy season.
• People should be made aware and motivated to keep water resources clean.

Question 5.
Explain the differences between pure air and polluted air.
Answer:
Pure air is free from harmful gases which can be poisonous in nature. Pure air has balanced quantity of all its constituent gases and it is free from other germs. This type of air is fit for breathing. On the other hand polluted air has poisonous gases and other suspended impurities like dust and smoke. It is unfit for consumption.

Question 6.
Explain circumstances leading to acid rain. How does acid rain affect us?
Answer:
Acid rain is caused due to mixing of poisonous gases with rain. When our industrial units emit poisonous gases like sulphur dioxide and nitrogen dioxide, these gases react with moisture present in air and form nitric acid and sulphuric acid. These acids fall on the earth with rain making rain water acidic and harmful.

Acid rain causes the corrosion of buildings and make food grains, fruits and vegetables on which it fall, unfit for consumption.

Question 7.
Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide
(c) Methane
(d) Nitrogen
Answer:
Sulphur dioxide.

Question 8.
Describe the ‘Green House Effect’ in your own words.
Answer:
Green house effect means warming the environment. When the rays of sun reach earth, some of the heat is absorbed by the earth. Rest of it is reflected back by the earth. Some of the heat is trapped by the environment of the earth. This causes warming of the environment, which is necessary for the sustaining life. This trapping of the heat is called green house effect.

Question 9.
Prepare a brief speech on global warming. You have to deliver the speech in your class.
Answer:
Continuous increase in the temperature of the earth is called global warming. It it caused by the pollution of air, excessive heat trapped by the green house gases, because the amount of green house gases has increased in the environment. Global warming is a threating phenomenon because we may have to face dire consequences due to Global warming.

Question 10.
Describe the threat to the beauty of the Taj Mahal.
Answer:
Increasing air pollution has posed a threat to the beauty of the Taj Mahal. Excessive poisonous gases and smoke has started to discolour the white marble of the Taj Mahal. Acid rains due to increasing air pollution has started to corrode the marble, thus making Taj Mahal loose its beauty.

Question 11.
Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Answer:
Addition of nutrients in water flourishes the growth of microorganisms like algae. When these microorganisms die, they become food of bacteria. When bacteria become active, they consume a lot of oxygen present in water. Decrease in oxygen in water, becomes trouble for other aquatic animals and they start dying due to insufficient amount of oxygen to breath.

Extended Learning – Activities and Projects

Question 1.
In some cities, a pollution check has been made compulsory for vehicles. Visit a petrol pump in order to learn about the process of conducting a pollution check. You may systematically record your findings in the following areas:
(i) Average number of vehicles checked per month.
(ii) Time taken to check each vehicle.
(iii) Pollutants checked for.
(iv) The process of testing.
(v) Permissible levels of emission of various gases.
(vi) Measures taken if the emitted gases are above the permissible limits.
(vii) How frequently is a pollution check required?
Answer:
For self attempt.

Question 2.
Conduct a survey in your school to investigate various environment related activities that have been undertaken. The class can divide itself into two groups, with each group looking at a different area. For example, one group can find out whether there is an environment club in the school. What are its objectives? What is its calendar of events? How can you become a member?
If your school does not have such a club, you can even think of starting one along with a few of your friends.
Answer:
For self attempt.

Question 3.
Organise a field visit to a river in or around your town with the help of your teachers. Observations followed by discussion could focus on:
(i) The history of the river.
(ii) Cultural traditions.
(iii) Role of the river in meeting the town’s water needs.
(iv) Pollution concerns.
(v) Sources of pollution.
(vi) Effects of pollution on the people living by the riverside as well as those living far away.
Answer:
For self attempt.

Question 4.
Find out with the help of your teachers and the internet (if possible), whether there are any international agreements to control global warming. Which are the gases covered under these agreements?
(i) www.edugreen.teri.res.in/explore/air/ air.htm
(ii) www.edugreen.teri.res.in/explore/water/ pollu.htm
(iii) www.cpcb.nic.in/citizen’s%Charter/ default_citizen’s.html
(iv) coe.mse.ac.in/kidswater.asp
(v) coe.mse.ac.in/kidsair.asp
Answer:
For self attempt.

HBSE 7th Class Science Pollution of Air and Water Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is a pollutant?
Answer:
Pollutant is an undesired and harmful substance.

Question 2.
What is air pollution?
Answer:
Addition of pollutants to air is called air pollution.

Question 3.
Name any two air pollutants.
Answer:
Smoke and sulphur dioxide.

Question 4.
Name any two natural pollutants.
Answer:
Forest fire and erruption in volcanoes.

Question 5.
What is smog?
Answer:
Mixture of smoke and moisture is called smog.

Question 6.
Name two chemicals causing acid rains.
Answer:
Sulphur dioxide and nitrogen dioxide.

Question 7.
Which gas is responsible for depletion of ozone layer?
Answer:
Chlorofluorocarbon.

Question 8.
Where CFC is used?
Answer:
CFC is used for refrigeration.

Question 9.
What effect does acid rain has on building?
Answer:
It corrodes the buildings.

Question 10.
Name any two green house gases.
Answer:
Methane and carbon dioxide.

Question 11.
Which phenomenon causes global warming?
Answer:
Green house effect.

Question 12.
Write any one harmful effect of global warming.
Answer:
It can cause flood by melting glaciers.

Question 13.
Which is the main constituent gas of air?
Answer:
Nitrogen about 78%.

Question 14.
What is the percentage of oxygen in air?
Answer:
21%.

Question 15.
Which industry is the main source of gaseous pollutants like sulphur dioxide and nitrogen dioxide?
Answer:
Petroleum refineries.

Question 16.
From what does the ozone layer – protect us?
Answer:
Ozone layer protects us from ultraviolet rays of sun.

Question 17.
What reduces the visibility in air?
Answer:
Small suspended particles emitted by automobiles using diesel as fuel.

Question 18.
Which refinery is producing pollutants near the Taj Mahal?
Answer:
Mathura oil refinery.

Question 19.
What is Marble cancer?
Answer:
Corrosion of marble due to acid rain is called marble cancer.

Question 20.
Which fuel is being used as the pollution free fuel?
Answer:
CNG and LPG.

Question 21.
What is trapping of radiations of sun by the atmosphere of the earth, called?
Answer:
Green house effect.

Question 22.
Which gas is mainly the green house gas?
Answer:
Carbon dioxide.

Question 23.
Which substances pollute water?
Answer:
Sewage, toxic chemicals, silt etc.

Question 24.
Name the Indian river which is considered as one of the ten most polluted rivers in world?
Answer:
Ganga.

Question 25.
What pollutes Ganga?
Answer:
Untreated sewage, dead bodies, garbage etc.

Question 26.
What is the plan, implemented to save Ganga, called?
Answer:
Ganga Action Plan.

Question 27.
Which chemicals released in water leads to toxicity in animals and plants?
Answer:
Arsenic, lead and fluorides.

Question 28.
What do you mean by potable water?
Answer:
Water which is suitable for drinking is called potable water.

Question 29.
Which chemical is used to purify water?
Answer:
Chlorine.

Question 30.
Which physical qualities should we look for in drinking water?
Answer:
Clearness, transparency and odour.

Short Answer Type Questions

Question 1.
Describe what is pollution.
Answer:
Pollution can be described as addition of unwanted and undesired harmful substances in any natural resource. Addition of these substances spoil the natural resources and make them unfit for consumption by men and other living beings. Air pollution, water pollution, soil pollution etc. are various types of pollutions.

Question 2.
Describe air pollution.
Answer:
Addition of poisonous and harmful substances in air is called air pollution. Air gets polluted when poisonous gases like sulphur dioxide, nitrogen dioxide and other oxides of nitrate get mixed up in air. It is also polluted by smoke emitted by industries using coal and also the smoke emitted by vehicles.

Question 3.
Write any three causes of air pollution.
Answer:
Following are various causes of air pollution:

• Smoke emitted due to fires in forests.
• Poisonous gases expelled the various industries.
• Poisonous gases emitted by vehicles using petroleum fuels.

Question 4.
What is smog? How is it produced?
Answer:
In winters, we can see a fog like dark layer in the mornings and nights. It reduces the visibility. This is called smog. Smog means fog plus smoke. It is formed due to combination of oxides of mitrates with fog. Various vehicles and industries produce smoke and the nitrates. Thus smog is formed.

Question 5.
What is ozone? How is it helpful for our environment?
Answer:
Ozone is a gas which is very helpful for environment of our earth. It forms a protective layer around the atmosphere of earth. It does not allow the ultraviolet rays of the sun from reaching the earth. U.V. rays can cause great damage to our earth. So, ozone is of great help for our earth.

Question 6.
What is ozone hole or depletion of ozone layer?
Answer:
A gas named ozone forms a protective layer around the atmosphere of the earth. It protects the earth from the ultra-violet rays of the sun. But some chemicals used in refrigeration causes damage to this layer. CFCs cause tearing away of this layer. This is called depletion of ozone layer. At some points, this layer is depleted completely and holes are created. These holes are called ozone holes.

Question 7.
What are the harmful effects of air pollution?
Answer:
Air pollution cause many diseases in human beings. Respiratory diseases are commonly caused by air pollution. It causes harm to our building and monuments. It reduces visibility as smog and causes many serious accidents.

Question 8.
How is acid rain caused?
Answer:
When rain water becomes acidic in nature, it is called the acid rain. Different industries produce pollutants like sulphur dioxide and nitrogen dioxide. These gases react with moisture and produce sulphuric acid and nitric acid. These acids fall on earth along with rain and this is called acidic rain.

Question 9.
What steps has. Honourable Supreme Court taken to save the Taj Mahal from air pollution?
Answer:
The Supreme Court has given orders that cleaner fuel be used in the near about areas of the Taj Mahal. Fuels like CNG and LPG are considered clean fuel. Moreover petrol should be free from lead. This is called unleaded petrol. Only unleaded petrol can be used in areas near the Taj Mahal.

Question 10.
What is the Green House effect?
Answer:
The sun sends its rays to the earth. Some of these rays are absorbed by the earth and some radiations are reflected back by the earth. Thes reflected radiations are not allowed to leave earth’s atmosphere completely. Some of these radiations are trapped by the earth’s atmosphere and this is called the green house effect.

Question 11.
What is global warming? How is it caused?
Answer:
Increasing temperature of the earth is called global warming. The radiation of the sun, reaching the earth is not being consumed. This is due to the deforestation. The level of CO₂ has increased and thus global warming has also increased. CO₂ is absorbed by the plants for photosynthesis. So reduced number of plants increases the amount of carbon dioxide in the environment, this causes accumulation of carbondioxide and increases temperature.

Question 12.
How does water get polluted?
Answer:
Water gets polluted when unwanted and harmful chemical substances are added to the water. Untreated sewer and garbage is also added to water resources to pollute water. All these chemicals make water unfit for usage.

Long Answer Type Questions

Question 1.
What is air pollution? How is it caused?
Answer:
When poisonous gases, dirt and smoke get added in the water it pollutes the air and it is called air pollution. Following factors are responsible for air pollution.
(i) Industrial Emissions : Various dangerous and poisonous gases emitted by different industries cause air pollution. Industries using coal and other petroleum products as fuel emit poisonous gases like sulphur dioxide and nitrogen dioxide. These gases further react with moisture present in environment and form their respective acids. These acids along with rain water cause acid rains.

(ii) Vehicles : Unburnt carbon particles emitted by vehicles due to incomplete combustion cause severe air pollution. It contains gases like carbodioxide and carbon monoxide which is highly poisonous. Unburnt carbon particles emitted as smoke also cause phenomenon like smog which reduce visibility besides causing air pollution.

(iii) Natural Pollutant: Natural pollutants like forest fire, volcanic erruption, dust storms etc. also cause air pollution to some extent.

(iv) Other activities of Man : Besides above described causes many other human activities also add to air pollution. Using fuels like cow dung, coal, wood etc. at home for domestic use also pollute the air. Agricultural practices like burning chaff after cultivation etc. also pollute the air. A lot of air pollution is caused due to burning of crackers on Diwali and other celebrations.

Question 2.
How is water pollution caused?
Answer:
Water pollution is caused by many factors. These pollutants are described below :
(i) Industrial discharges: Various harmful and poisonous chemicals are discharged by various industries directly into water bodies. These chemicals when added in water, spoil it and render it unfit for consumption by living beings.

(ii) Domestic discharges : Sewage from homes are collected and disposed off in rivers nearby. This untreated sewage is one of the prominent causes of water, pollution.

(iii) Religious Rituals : Various religious rituals of different religions also add to certain extent to the water pollution.

Dispersion of dead bodies or remains of dead bodies in rivers is causing pollution of water. Various other materials are also dispersed in water after performing some rituals. These also make water dirty.

(iv) Other Human activities : Apart from above cited reasons, water is also polluted due to certain other human activities. People wash their clothes on banks of rivers. They take their livestock to rivers for their bathing. They throw their wastage in water bodies and sometimes defecate in open at the banks of rivers. This makes water polluted and unfit for human consumption.

Question 3.
What measures should be taken to control air pollution and water pollution?
Answer:
Air pollution and water pollution are causing a great threat for the human civilization. We should seriously work to control them. Following measures can help us in controlling air and water pollution :
(i) All industrial units should use cleaner fuels and should not release their harmful 4 emission directly into air or water.

(ii) All industrial units throwing their harmful waste products in water, should install treatment or purification plants in their premises so that only treated and purified waste should be released in water bodies.

(iii) All the sewages of cities and villages should treated to destroy harmful physical, chemical and biological impurities before releasing it in water resources.

(iv) All vehicles should use pollution free fuels like CNG, LPG and unleaded petrol. Vehicles should be serviced well to avoid incomplete combustion of fuel.

(v) Smokeless fuels should be provided for domestic usage.

(vi) Electrical crematoriums should be made in all cities as well as in villages.

Question 4.
What are the various harmful effects of air and water pollution?
Answer:
(i) Air and water pollution are both dangerous for human health. They cause various diseases, which are the result of harmful emissions and discharges in air and water. Water brone diseases like Cholera, Typhoid, Infections, etc. are caused. Air pollution causes various respiratory diseases like asthma, allergies and lung cancer etc.

(ii) These pollutions also cause troubles for animals. Water pollution destroy the aquatic life as it causes deficiency of oxygen in water causing death of aquatic animals.

(iii) Various environmental problems like global warming are result of air pollution. Due to increase in level of carbon dioxide, the radiations of sun are not allowed to leave our environment. They get trapped in our environment and temperature of earth gets increased. This is called global warming.

(iv) Fresh and consumable water is getting reduced day by day as water resources are getting polluted very rapidly.

(v) Phenomena like smog, marble-cancer etc. are causing threat to our property and life.

Pollution of Air and Water Class 8 HBSE Notes

• Addition of unwanted and poisonous substances in air or water is called their respective pollutions.
• Air and water pollution has increased in recent past with industrialization and urbanization.
• Air is a mixture of gases mainly the nitrogen, oxygen and carbon dioxide when any of the harmful gases increase in its percentage, it makes the air polluted.
• Emission of smoke in industries, smoke due to forest fires and smoke emitted by vehicles pollutes the air.
• Smoke, dust of harmful gases emitted during volcanic erruptions, or forest fires or due to dust storms etc. are called the natural air pollutents.
• Unburnt fuel of the vehicles is one of main cause of air pollution.
• Air pollution can give rise to different ailments in human beings. Oxides of nitrogen can cause asthma, cough and wheezing. It can even cause cancer of lungs.
• Pollutants like sulphur dioxide, nitrogen oxide are emitted by industries.
• Gases used in refregeration also cause depletion of ozone layer, which cause further environmental problems like global warming.
• Non-living objects are also effected by air pollution. Discolouring of white marble of Taj Mahal is an example.
• Deforestation is one of the main cause of air pollution because less amount of carbon dioxide is absorbed by the plants and its amount increases in atmosphere resulting in global warming.
• Addition of undesirable substances like sewage, harmful chemicals etc. to the water cause water pollution.
  Polluted water becomes unfit for consumption.
• Water is purified before consuming it.

Haryana State Board HBSE 7th Class Science Solutions Chapter 10 Respiration in Organisms Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 10 Respiration in Organisms

HBSE 7th Class Science Respiration in Organisms Textbook Questions and Answers

Question 1.
Why does an athlete breathe faster and deeper than usual after finishing the race?
Answer:
During the race, the athlete has to run very fast. The demand for energy at that time increases, which increase the demand for more supply of oxygen, so, athlete has to breathe faster and deep to inhale more oxygen.

Question 2.
List the similarities and differences between aerobic and anaerobic respiration.
Answer:
Differences between aerobic and anaerobic respiration :

Similarities : (Both aerobic and anaerobic respiration produce energy and give out carbon dioxide.

Question 3.
Why do we often sneeze when we inhale, a lot of dust-laden air?
Answer:
We sneeze to get rid of the unwanted particles like dust etc from our body. It allows only clean and dust free air to enter our body.

Question 4.
Take three test tubes. Fill 3/4th of each tube with water. Label them A, B and C. Keep a snail in test tube A; a water plant in test tube B and in C, keep snail and plant both. Which test tube will have highest concentration of CO₂?
Answer:
There will be highest concentration of CO₂ in tube A.

Question 5.
Tick the correct answer :
(a) In cockroaches air enters the body through :
(i) Lungs
(ii) Gills
(iii) Spiracles
(iv) Skin
Answer:
(iii) Spiracles

(b) During heavy exercise, we get cramps in the legs due to the accumulation of :
(i) carbon dioxide
(ii) lactic acid
(iii) alcohol
(iv) water
Answer:
(ii) lactic acid

(c) Normal range of breathing rate per minute in an average adult person at rest is :
(i) 9-12
(ii) 15-18
(iii) 21-24
(iv) 30-33
Answer:
(ii) 15-18

(d) During exhalation, the ribs :
(i) move outwards
(ii) move downwards
(iii) move upwards
(iv) do not move at all
Answer:
(ii) move downwards.

Question 6.
Match the items in column I with those in column II.

Answer:
(a) (iii)
(b) (iv)
(c) (i)
(d) (v)
(e) (ii)
(f) (vi).

Question 7.
Make ‘T’ if the statement is true and ‘f if it is false.
(i) During heavy exercise the breathing rate of a person slows down. (T/F)
(ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/F)
(iii) Frogs breathe through their skins as well as their lungs. (T/F)
(iv) The fishes have lungs for respiration. (T/F)
(v) The size of the chest cavity increases during inhalation. (T/F)
Answer:
(i) False
(ii) False
(iii) True
(iv) False
(v) True.

Question 9.
Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction – upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

(i) The air tubes of insects.
(ii) Skeletal structures surrounding chest cavity.
(iii) Muscular floor of chest cavity.
(iv) Tiny pores on the surface of leaf.
(v) Small openings on the sides of the body of an insect.
(vi) The respiratory organs of human beings.
(vii) The openings through which we inhale.
(viii) An anaerobic organism.
(ix) An organism with tracheal system.
Answer:
(i) Trachea
(ii) Ribs
(iii) Diaphragm
(iv) stomata
(v) spiracles
(vi) lungs
(vii) nostrils
(viii) yeast
(ix) ant.

Question 10.
The mountaineers carry oxygen with them because :
(a) At an altitude of more than 5 km there is no air.
(b) The amount of air available to a person is less than that available on the ground.
(c) The temperature of air is higher than that on the ground.
(d) The pressure of air is higher than that on the grow.
Answer:
(b) The amount of air available to a person is less than that available on the ground.

Extended Learning – Activities and Projects

Question 1.
Observe fish in an aquarium. You will find flap like structures on both sides of their heads. These are flaps which cover the gills. These flaps open and close alternately. On the basis of these observations, explain the process of respiration in the fish.
Answer:
Do yourself. Take help your teacher.

Question 2.
Visit a local doctor. Learn about the harmful effects of smoking. You can also collect material on this topic from other sources. You can seek help of your teacher or parents. Find out the percentage of people of your area w ho smoke. If you have a smoker in your family, confront him with the material that you have collected.
Answer:
Do yourself.

Question 3.
Visit a doctor. Find out about artificial respiration. Ask the doctor:
(a) When does a person need artificial respiration?
(b) Does the person need to be kept on artificial respiration temporarily or permanently?
(c) From where can the person get supply of oxygen for artificial respiration?
Answer:
Do yourself.

Question 4.
Measure the breathing rate of the members of your family and some of your friends. Investigate :
(a) If the breathing rate of children is different from that of adults.
(b) If the breathing rate of males is different from that of females.
If there is a difference in any of these cases, try to find the reason.
Answer:
Do yourself.

HBSE 7th Class Science Respiration in Organisms Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is respiration?
Answer:
Respiration is a process of taking oxygen into the cells to break down simple food materials to release energy.

Question 2.
What is breathing?
Answer:
Breathing is inhaling oxygen and exhaling carbon dioxide.

Question 3.
Where does cellular respiration take place?
Answer:
Cellular respiration takes place inside the cells of the body.

Question 4.
What is aerobic respiration?
Answer:
Process of respiration taking place in the presence of oxygen is called aerobic respiration.

Question 5.
What is anaerobic respiration?
Answer:
Process of respiration without the presence of oxygen is called anaerobic respiration.

Question 6.
Does the process of anaerobic respiration take place in human body?
Answer:
Yes, during heavy physical activities, when supply of oxygen is not sufficient, anaerobic respiration takes place in the muscle cells.

Question 7.
What is diaphragm?
Answer:
Diaphragm is a large muscular sheet which forms the floor of the chest cavity.

Question 8.
Name the main respiratory organs in mammals.
Answer:
Lungs are the main respiratory organs in the mammals.

Question 9.
Name the main respiratory organs in insects.
Answer:
Spiracles and tracheae are the main respiratory organs in insects.

Question 10.
Name the respiratory organs in the fish.
Answer:
Gills are the respiratory organs in the fish.

Question 11.
How does earthworm respirate?
Answer:
Earthworm respires through its moist skin.

Question 12.
Where does exchange of gases take place in plants?
Answer:
In plants the exchange of gases takes place through tiny openings called stomata on the leaves.

Short Answer Type Questions

Question 1.
Differentiate between breathing and respiration.
Answer:
Breathing and respiration have following differences:

Question 2.
How does aerobic respiration takes place?
Answer:
In aerobic respiration oxygen is taken into the cells. The food is broken down into simple food materials and energy is released. Carbon dioxide and water is also released.
Gulcose \(\frac{\text { presence of }}{\text { Oxygen }}\) Carbon dioxide + water + energy

Question 3.
What is breathing rate? How is it counted and what is the breathing rate in an adult at the position of rest?
Answer:
Breathing rate is the number of times a person breathes in a minute. To count the breathing rate, we have to count an inhalation and an exhalation as one. Breathing rate in an adult at rest is 15-18 times in a minute.

Question 4.
How is air pushed out during exhalation?
Answer:
During exhalation the ribs move downwards and inwards. The diaphragm moves up and chest cavity gets contracted and air is thrown out.

Question 5.
How do insects breathe?
Answer:
Insects have small openings on the outside of their bodies. These openings are called spiracles, which are connected to the air pipes called tracheae. In tracheae the exchange of gases take place.

Question 6.
How are frogs peculiar in their way of breathing?
Answer:
Frogs breathe differently in water and differently on land. They use their moist skin to breathe in water. They use lungs to breathe on land.

Question 7.
How do plants respirate?
Answer:
Plants also take in oxygen and give out carbon dioxide for respiration. They have small openings called stomata on the surface of there leaves. Exchange of gases take place through these openings.

Long Answer Type Questions

Question 1.
Explain the process of respiration.
Answer:
In respiration, there is a gaseous exchange between the organism and the environment. The process of respiration can be divided in two parts. Breathing and cellular respiration.

Breathing or external respiration: Oxygen is inhaled and Carbon dioxide is exhaled during breathing. This process takes place out side the cells and, thus is called external breathing.

Cellular respiration or internal respiration : This is a biochemical process which takes place inside the cells of the body. In this process food i.e. glucose is broken into simpler forms. Energy is released during this process which is used by body to perform various functions. Carbon dioxide and water is also released. The Carbon dioxide is expelled out during breathing.
Food + Oxygen → Carbon dioxide + Water + Energy.

Question 2.
Explain the process of respiration in plants.
Answer:
In plants the process of respiration leads to the release of energy. It is a cellular process in which molecules of glucose break down in the presence of oxygen to release energy along with water and carbon dioxide. Exchange of gases take place through small openings on the surface of the leaves. These are called stomata. Lower plants lack the organs of breathing. In such plants gaseous exchange occurs due to simple process of diffusion. The rate of exchange of gases in plants is not as fast as in animals.

Respiration in Organisms Class 7 HBSE Notes

• Respiration is a process of taking oxygen into the cells in order to break down simple food materials to release energy and eliminate waste products.
• Breathing is inhaling oxygen and exhaling carbon dioxide.
• Breathing takes place out side the cells.
• Cellular respiration takes place inside the cells.
• Inside the Cells the food is broken into water and carbon dioxide. This is called cellular respiration. This process releases a lot of energy.
• When the process of respiration takes place in the presence of oxygen, it is called aerobic respiration.
• When the process of respiration takes place in the absence of oxygen, it is called anaerobic respiration.
• Human beings have a fully developed respiratory system.
• Nostrils inhale oxygen, which reaches the lungs through the nasal cavity.
• Lungs are organs, where the exchange of gases takes place. Carbon dioxide is expelled out and oxygen is consumed for cellular respiration.
• Smaller animals like cockroaches have structures called spiracles, for breathing. Earthworms breathe through their skin and fish have gills for respiration.
• In both plants and animals, mitochondria is the site of respiration.

Haryana State Board HBSE 7th Class Science Solutions Chapter 11 Transportation in Animals and Plants Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 11 Transportation in Animals and Plants

HBSE 7th Class Science Transportation in Animals and Plants Textbook Questions and Answers

Question 1.
Match structures given in column I with functions given in column II.

Answer:
(i) (b)
(ii) (d)
(iii) (a)
(iv) (c)

Question 2.
Fill in the blanks :
(i) The blood from the heart is transported to all parts of the body by the __________.
(ii) Haemoglobin is present in __________ cells.
(iii) Arteries and veins are joined by a network of __________.
(iv) The rhythmic expansion and contraction of the heart is called __________.
(v) The main excretory product in human beings is __________.
(vi) Sweat contains water and __________.
(vii) Kidneys eliminate the waste materials in the liquid form called __________.
(viii) Water reaches great heights in the trees because of suction pull caused by __________.
Answer:
(i) Arteries
(ii) Red Blood Cells
(iii) Capillaries
(iv) Heart beat
(v) Urine
(vi) Urea
(vii) Urine
(viii) Transpiration

Question 3.
Choose the correct options:
(а) In plants, water is transported through :
(i) Xylem
(ii) Phloem
(iii) Stomata
(iv) Root hair
Answer:
(i) Xylem

(b) Water absorption through roots can be increased by keeping the plants :
(i) in the shade
(ii) in dim light
(iii) under the fan
(iv) covered with a polythene bag.
Answer:
(iii) under the fan

Question 4.
Why is transport of materials necessary in a plant or an animal? Explain.
Answer:
Transport of materials is necessary in plant or animal because due to it the nutrients are made available to all the parts of the body. If the transport of necessary nutrients does not take place in the body, the body will not be able to survive. So, the circulation of nutrients takes place in the whole body through the process of transportation.

Question 5.
What will happen if there are no platelets in the blood?
Answer:
The blood platelets are responsible for the clotting of the blood. When some injury occurs blood starts flowing. But it clots on its own due to the blood platelets. If there are no platelets in the blood, the blood will not be able to clot and keep on flowing through a wound or injury. This can prove fatal for the organisms as no blood will remain in the body.

Question 6.
What are stomate? Give two functions of stomata.
Answer:
There are small openings on the lower surface of the leaves and stems. These pores are called stomata. These opening are covered with guard cells. Two functions of stomata are:

• It helps in the transpiration of water i.e. the loss of excess water from the plant.
• Loss of water from the stomata creates an upward pull i.e a suction pull which helps in absorption of water to great height in tall trees.

Question 7.
Does transpiration serve any useful function in the plants? Explain.
Answer:
Transpiration is an important function in plants. It serves the following purposes:

• It helps to enhance the absorption of water by creating a suction pull.
• It helps the plant in getting rid of the excess water.
• It produces a cooling effect on the plant which prevents the heat of the sun light from damaging plants.
• It helps in transport of water and minerals to leaves and leaves use the water for the process of photosynthesis.

Question 8.
What are the components of blood?
Answer:
There are four components of the blood.

• Plasma is the liquid part of the blood which is yellowish in colour and contains 90 percent water. It contains food, enzymes, wastes and proteins etc.
• Red blood cells (R.B.Cs) are disc shaped cells containing red coloured pigment called haemoglobin in it. Haemoglobin helps in transportation of oxygen.
• White blood cells (W.B.Cs) are the fighting cells, which protect us against bacteria and foreign material causing infections
• Platelets help in clotting of the blood.

Question 9.
Why is blood needed by all the parts of a body?
Answer:
Blood is needed by all parts of the body because, it contains the digested food in it. It supplies the digested food to various parts of the body and provide essential energy to them. This energy helps the body to perform various functions and activities.

Question 10.
What makes the blood look red?
Answer:
A red coloured pigment called haemoglobin gives the blood its red colour. This pigment helps in carrying oxygen to various part of the body by blood.

Question 11.
Describe the function of the heart.
Answer:
The heart functions in the following way:
The right auricle and ventricle receives blood with carbon dioxide from all the parts of the body. The collected blood is then pumped to the lungs for the purification. In lungs the exchange of gases take place and purified blood is sent back to the left auricle. It pumps it to the left ventricle, which in turn pumps off the purified blood to all the parts of the body through arteries.

Question 12.
Why is it necessary to excrete waste products?
Answer:
The build up of waste and poisonous products in our body is always harmful. The waste products like urea etc. are toxic. When such toxic materials are not removed from the body, they get mixed with blood and can damage the cells of the body, thus proving fatal. It is, therefore, necessary to remove such poisonous waste materials from our body.

Question 13.
Draw a diagram of the human excretory system and label the various parts.
Answer:
Do it yourself.

Extended Learning – Activities and Projects

Question 1.
Find out about blood groups and their importance.
Answer:
Do it yourself.

Question 2.
When a person suffers from chest pain, the doctor immediately takes an ECG. Visit a doctor and get information about ECG. You may even look up an encyclopaedia or the internet.
Answer:
Do it yourself.

HBSE 7th Class Science Transportation in Animals and Plants Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is circulatory system?
Answer:
Circulatory system is that system which transport nutrients to various parts of the body.

Question 2.
What makes the blood red?
Answer:
A red pigment called haemoglobin makes the colour of the blood red.

Question 3.
Name various kinds of cells present in blood.
Answer:
Blood has liquid part called plasma which has Red Blood Cells, white blood cells and platelets in it.

Question 4.
What role does the red pigment haemoglobin play in our body?
Answer:
Haemoglobin gets bound with the oxygen and supplies oxygen to various parts of the body. Oxygen is essential for respiration.

Question 5.
Why platelets are important for humans?
Answer:
Platelets are very important because they cause clotting of the blood. Without platelets blood will flow from the wounds unstopped and cause death.

Question 6.
What is pulse?
Answer:
Number of times the heart beats in a minute is called pulse. In resting position pulse rate of a normal human is 72-80 beats/min.

Question 7.
What is the main difference between an artery and a vein?
Answer:
Artery carries purified blood i.e. blood carrying oxygen and vein carries blood rich in carbon dioxide.

Question 8.
What is transpiration?
Answer:
Transpiration is the loss of excess water from the leaves through the small pores called stomata.

Question 9.
What is excretion?
Answer:
Excretion is the process of throwing out the unwanted and waste products from the body.

Question 10.
What is dialysis?
Answer:
Dialysis is a process of separating small molecules from the large molecules using a semipermeable membrane.

Short Answer Type Questions

Question 1.
Explain briefly how the following are transported in plants.
(a) Water and mineral
(b) Food
Answer:
(a) Water and minerals are transported through the vascular tissues called xylem. Roots absorbs water from the soil and xylem transport it leaves prepare food by photosynthesis and this food is transported from leaves to different part by phloem.

(b) Food is transported in plants through vascular tissue called phloem.

Question 2.
What is transpiration? How is it different from translocation?
Answer:
Transpiration is the process of loosing excess water from the plants through small pores present on leaves called stomata. While the process of transportation of food through phloem is called translocation. Phloem transfer glucose from leaves to other parts of the plant while transpiration is evaporation of water to the environment.

Question 3.
List the factors affecting transpiration.
Answer:
Following factors affect transpiration in plants :
(i) Sunlight : Bright sunlight fastens the process of transpiration. No transpiration takes place during night.

(ii) Temperature : High temperature increases the rate of-transpiration while low temperature lowers the rate of transpiration.

(iii) Wind : Blowing wind increases the transpiration as water vapours are quickly removed from the leaves.

(iv) Humidity: Humid day lessens the rate of transpiration.

Question 4.
How does transportation occur in lower animals?
Answer:
The transportation occurs in lower animals through diffusion. The nutrients circulate in the body of lower animals by the flow of cytoplasm. In some multicellular aquatic plants transportation takes place by water which circulates the nutrients through their bodies.

Question 5.
What is stethoscope? What are its main parts?
Answer:
Stethoscope is an instruments used to measure the heart beat by the doctors. It has three parts :

• a chest piece that is sensitive to heart beats.
• two ear pieces.
• a tube joining the chest piece and ear pieces.

Question 6.
Write a short note on heart beat and pulse?
Answer:
Number of times a heart beats in a minute is called pulse. It can be felt by feeling the pressure of movement of blood through the artery at our wrist and by feeling the thumping of heart in our chest. It increases with physical activities. In children it varies from 90 to 100 times per minute and in adults from 70-72 beats per minute.

Question 7.
Mention the functions of the blood.
Answer:
Blood performs the following functions

• It transports nutrients to various parts of body.
• It carries oxygenated blood to different parts of the body.
• It collects deoxygenated blood from various parts of the blood and takes it to lungs for purification.
• It maintains the body temperature.
• White blood cells fight against the infections and protect us from diseases.

Question 8.
Name various organs of excretion in humans.
Answer:
Various organs of excretion in humans are :

• Lungs – for exchange of gases.
• Skin – for sweating.
• Large intestine – for excretion faeces.
• Kidneys – for excretion urine.
• Liver – for excretion excess sugar.

Question 9.
What is the importance of sweating?
Answer:
Sweat is water, salt and urea eliminated by skin in liquid form. The sweat is secreted by the sweat glands. Sweat is important in expelling the wastes like urea and salt from the body, It keeps the body cool and maintain the body temperature.

Question 10.
Explain the process of dialysis in brief.
Answer:
Process of Dialysis is used to remove the waste from the body of those people, whose kidneys are not working. Dialyses machine help in removing the waste. A tube of the machine is connected to patients blood. Blood is purified in a semipermeable membrane inside the machine and purified blood is sent back to the body.

Long Answer Type Questions

Question 1.
Explain the circulatory system in Human beings.
Answer:
The Human circulatory system consists of mainly three parts : (i) Heart, 2. Blood vessels, 3. Blood.
1. The Heart: Heart is the pumping organ present in our body. It pumps blood to all the parts of the body. It equals a clenched fist in its size. It is located in the chest cavity on the left side. It is made up of muscles and protected by a cardial membrane called paracardium. It has four chamber – two upper chambers called Auricles and two lower chambers called Ventricles. Blood is received by auricles and pumped by ventricles. The contraction and relaxations of these chambers is called the heart beat.

2. Blood vessels : Arteries, veins and capillaries are three types of blood vessels. Arteries carry oxygenated blood while veins collect deoxygenated blood. All arteries and veins are interconnected through the network of capillaries.

3. Blood : It is red coloured fluid carrying digested food to all the parts of the body and waste products to the excretory system. It has fluid portion called plasma. Plasma has Red blood cells, White blood cells and platelets in it. Red colour of the blood is due to the red pigment called haemoglobin in it. White blood cells fight against infections and platelets cause clotting of the blood.

Question 2.
Explain the Excretory System of human beings.
Answer:
Human Excretory System consists of following organs:

• A pair of Kidneys
• Ureters
• Urinary bladder
• Urethra.

→  Kidneys : Kidneys are bean shaped structures, located on each side of the backbone above the waist. Kidneys have a number of coiled tubes like structures called nephrons. Nephron consists of a Bowman’s Capsule. It is a cup like structure having a network of blood capillaries. Nephron has a long tubule surrounded by renal capillaries. Nephrons filter the excess of water salt, urea from the blood passing through it. This waste in liquid form is called urine.

→ Ureters : Ureters are long tubes passing urine formed in the kidneys to the urinary bladder. Both kidneys send a ureter to the urinary bladder.

→ Urinary bladder : Urinary bladder is an elastic sac like structure which collects the urine from ureters. Urine remains stored in it until excreted.

→ Urethra : Urethra is the opening through which the urine is passed out of the body.

Question 3.
Explain the process of transport of substances in plants.
Answer:
In plants water and minerals is transported to the leaves and other parts and similarly food is transported from leaves to all the parts of the plant.

Transport of material in plants take place through vascular tissues. There are two types of vascular tissues in plants called xylem and phloem. Xylem forms a continuous network of channels. This connects roots to the leaves through stems and through branches. This network is used to supply water and minerals to the various parts of the body. The roots absorb water from the soil and transport it to leaves and branches through xylem. This is called ascent of sap. Similarly a network of channels use to transport the food prepared by the leaves to the other parts of the plants is called phloem. This process is called translocation.

Transportation in Animals and Plants Class 7 HBSE Notes

• Every organism needs food and water to survive.
• Food and water is supplied to all parts of the bodies of the organisms by the transportation of these substances.
• Transportation of materials in human body is conducted by the circulatory system.
• Circulatory system in human beings consists of three organs : Blood, Blood vessels and Heart.
• Blood is the liquid which carries the digested food to various parts of the body.
• Blood contains liquid portion called plasma, Red blood cells, white blood cells and platelets.
• Red blood cells carry a red pigment called hemoglobin. Hemoglobin gives red colour to the blood and is responsible for carrying oxygen to all parts of body.
• White blood cells fight against the infections in our body.
• Platelets cause clotting blood.
• Blood vessels are of two types : Arteries carrying oxygenated blood to all parts of the body and veins collect deoxygenated blood from various parts of the body and take it to heart.
• Arteries and veins are interconnected with thin tubes called capillaries.
• In plants, vascular tissues are responsible for transporting food, water and minerals to the various parts of the plant.
• Xylem carries absorbed water and mineral to all parts of plant, while phloem carries food from leaves to the rest of the plant.
• After the process a digestion our body produces some waste products – these wastes are thrown out of the body and this is called excretion.
• In humans, kidneys are the main excretory organs.
• In plants excess water is thrown out by transpiration.
  Transpiration is the process of loosing excess water by evaporation through small opening on the surface of leaves called stomata.
• Dialysis is conducted to remove waste from humans body with damaged kidneys.

Haryana State Board HBSE 7th Class Science Solutions Chapter 12 Reproduction in Plants Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 12 Reproduction in Plants

HBSE 7th Class Science Reproduction in Plants Textbook Questions and Answers

Question 1.
Fill in the blanks :
(a) Production of new individuals from the vegetative part of parent is called _________.
(b) A flower may have either male or female reproductive parts. Such a flower is called _________.
(c) The transfer of pollen grains from the anther to the stigma of the same or of another flower of the same kind is known as _________.
(d) The fusion of male and female gametes is termed as _________.
(e) Seed dispersal takes place by means of _________ and _________.
Answer:
(a) vegetative reproduction,
(b) bisexual flower
(c) pollination
(d) fertilization,
(e) wind, water, insects.

Question 2.
Describe the different methods of asexual reproduction. Give examples.
Answer:
Different methods of asexual reproduction are :
(a) Binary fission : This process takes place in unicellular organisms. Parent cell elongates and get divided into two identical daughter cells. Each daughter cell grows into an independent adult, e.g. in case of bacteria.

(b) Endospore formation : In this method a spore wall is formed around a bacterial cell to form an endospore. This endospore germinates to form an active bacterium under favourable conditions.

(c) Fragmentation : This occurs mainly in Algae. Body of the organism breaks up into two parts. Then each part grows into a new filament thus forming two organisms from a single one.

(d) Spore formation : The spores are tiny, spherical unicellular structures protected by a thick wall. The spores are stored in a hard outer covering and this is called sporangia. Under favourable conditions the hard cover breaks and spores spread for germination.

(e) Budding : In yeast, new organisms are produced by the bud formation from the parent organism. After growing to full size, the bud gets detached and form a new independent individual.

(f) Vegetative reproduction : When vegetative part of a plant like stems, leaves and root etc. give rise to new ones, it is called vegetative reproduction.

Question 3.
Explain what do you understand by sexual reproduction?
Answer:
Sexual reproduction means involvement of two parents in the process of reproduction. It is found mainly in higher plants. Male gamete and female gamete fuse to form a zygote. These zygotes develop into individuals which are not identical. Offspring inherit the characteristics of both the parents. In sexual reproduction both parents survive after the process of reproduction.

Question 4.
State the main differences between asexual and sexual reproduction.
Answer:

Question 5.
Sketch the reproductive parts of a flower.
Answer:

Question 6.
Explain the difference between self-pollination and cross-pollination.
Answer:

Question 7.
How does the process of fertilization take place in flowers?
Answer:
When the pollen grain reaches the stigma of a same flower, it starts growing out in pollen tube of the stigma. This tube continues to grow inside the style till it reaches the ovule. Male cells are released in the ovule for the fertilization with female cells and thus the zygote is formed. After this process of fertilization, the ovary develops into fruit and ovule into seeds.

Question 8.
Describe the various ways by which seeds are dispersed.
Answer:
Following are the ways in which the seeds get dispersed:
(i) Some light seeds like that of Madar, which are hairy, dry and small are carried away by the wind to different places. Some seeds having winged structure e.g. that of Maple and Drumstick are also dispersed by air.

(ii) Spiny seeds and fruits like that of Xanthium and Gokhru, the seeds stick to the clothes of passers-bye and animals. These seeds are carried away by these agents to different places.

(iii) In some cases having heavy seeds like that of Coconut, water acts as the dispersing agents.

(iv) Some seeds are diprersed when the fruit bursts like in case of Balsam and castor.

Question 9.
Match the items in Column I with those of Column II :

Answer:
(a) (iii)
(b) (v)
(c) (ii)
(d) (i)
(e) (iv)

Question 10.
Tick (✓) the correct answer :
(a) The reproductive part of a plant is the :
(i) Leaf
(ii) Stem
(iii) Root
(iv) Flower
Answer:
(iv) Flower

(b) The process of fusion of the male and the female gametes is called :
(i) fertilization
(ii) Pollination
(iii) reproduction
(iv) seed formation
Answer:
(i) fertilization

(c) Mature ovary forms the:
(i) Seed
(ii) Stamen
(iii) Pistil
(iv) Fruit
Answer:
(iv) Fruit

(d) A spore producing plant is :
(i) Rose
(ii) Bread mould
(iii) Potato
(iv) Ginger
Answer:
(ii) Bread mould

(e) Bryophyllum can reproduce by its :
(i) Stem
(ii) Leaves
(iii) Roots
(iv) Flower
Answer:
(ii) Leaves

Extended Learning-Activities and Projects

Question 1.
Make your own cactus garden by collecting pieces cut from different kinds of cacti. Grow the variety in one single flat container or in separate pots.
Answer:
Do it yourself.

Question 2.
Visit a fruit market and collect as many local fruits as possible. If many fruits are not available, you can collect tomatoes and cucumbers (these are fruits, though we use them as vegetables). Make drawings of the different fruits. Split the fruits and examine the seeds within. Look for any special characteristics in the fruits and their seeds.
Answer:
Do it yourself.

Question 3.
Think of ten different fruit-bearing plants. Remember that many vegetables are also fruits of the plants. Discuss with your teacher, parents, farmers, fruit growers and agricultural experts (if available nearby) and find out the manner of their dispersal. Present your data in the form of a table as shown below :

Answer:
Do it yourself.

Question 4.
Suppose there is one member of a particular kind of organism in a culture dish, which doubles itself in one hour through asexual reproduction. Work out the number of members of that kind of organism which will be present in the culture dish after ten hours. Such a colony of individuals arising from one parent is called a “clone”.
Answer:
Do it yourself.

HBSE 7th Class Science Reproduction in Plants Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What do you understand by the term reproduction?
Answer:
Reproduction is the process by which the living organisms produce more of their ownkind.

Question 2.
Name the methods by which plants reproduce.
Answer:
Plants reproduce in two ways :

• Asexual reproduction
• Sexual reproduction.

Question 3.
What is pollination?
Answer:
Pollination is a process in which pollen grains get transferred from anther to the stigma of the‘flower.

Question 4.
Name different methods of asexual reproduction.
Answer:
Various methods of asexual reproduction are :

• Binary fission
• Endospore formation
• Fragmentation
• spore formation
• Budding
• Vegetative reproduction.

Question 5.
What do you mean by the term fertilization?
Answer:
Fertilization is a process in which fusion of male and female gametes takes place to produce the zygote.

Question 6.
What is vegetative reproduction?
Answer:
It is the simplest method of reproduction in plants. In this method the vegetative parts like stem, roots and leaves produce new ones.

Question 7.
What is the advantage of the vegetative reproduction?
Answer:
The vegetative reproduction occurs very fast and easily. So quick reproduction is possible.

Question 8.
What is difference between unisexual and bisexual flowers?
Answer:
Unisexual flower has either a male or female reproductive part and bisexual flower has both of them.

Question 9.
Write any one advantage of seed dispersal.
Answer:
It prevents the plants from competing for sunlight, water and minerals.

Question 10.
Where are the male and female gametes found?
Answer:
The male gametes are found inside the pollen grains and the ovule contains the female gametes.

Short Answer Type Questions

Question 1.
What is reproduction? Name various methods of reproduction in plants.
Answer:
Reproduction is the process by which the living organisms produce more of their ownkind. Plants reproduce by two methods asexual and sexual. Asexual reproduction means the birth of new ones by single parent only. Sexual reproductions means involvement of two parents in the process.

Question 2.
List the different methods of asexual reproduction. In which type of plants does asexual reproduction occur?
Answer:
Asexual reproduction occurs in lower form of plants, where they do not have any reproductive part. It occurs through following methods.

• Binary fission
• Budding
• Endospore formation
• Spore formation
• Fragmentation
• Vegetative reproduction.

Question 3.
What is pollination? How is it brought about?
Answer:
The transfer of pollen grains from anther to stigma of a flower is called pollination. Pollination is brought about by many agents like water, air, animals and insects. Pollen grains are carried by these agents from anther of one flower to the stigma of another flower of same kind.

Question 4.
What do you mean by cross-pollination and self-pollination?
Answer:
Transfer of pollens occur in two ways. When pollen grains ate transferred to stigma of the same flower, it is called self pollination. When transfer of pollen grains take place from anther of one flower to the stigma of another flower of same kind, it is called cross pollination.

Question 5.
Write a short note on vegetative propagation.
Answer:
Vegetative reproduction! means the birth of new ones from the vegetative parts of the plant like leaves, stem, roots and buds. This is an asexual type of reproduction. Eyes on potato, buds sprouting on the leaves of bryophyllum, new plant growing out of cactus’ stem etc are examples of vegetative reproduction.

Question 6.
Write atleast three advantages of vegetative propagation methods.
Answer:
Following are the advantages of vegetative propagation:

• It is a fast method of reproduction.
• Plants produced by vegetative propagation have same features as that of parent plant.
• Plants produced by vegetative reproduction bear flowers and fruits earlier than the plants grown out of seeds.

Long Answer Type Questions

Question 1.
What is Asexual reproduction? Explain various methods of asexual reproduction.
Answer:
Asexual reproduction means obtaining new plants from one parent without seeds. Various methods of asexual reproduction are as follows :

Different methods of asexual reproduction are :
(a) Binary fission : This process takes place in unicellular organisms. Parent cell elongates and get divided into two identical daughter cells. Each daughter cell grows into an independent adult, e.g. in case of bacteria.

(b) Endospore formation : In this method a spore wall is formed around a bacterial cell to form an endospore. This endospore germinates to form an active bacterium under favourable conditions.

(c) Fragmentation : This occurs mainly in Algae. Body of the organism breaks up into two parts. Then each part grows into a new filament thus forming two organisms from a single one.

(d) Spore formation : The spores are tiny, spherical unicellular structures protected by a thick wall. The spores are stored in a hard outer covering and this is called sporangia. Under favourable conditions the hard cover breaks and spores spread for germination.

(e) Budding : In yeast, new organisms are produced by the bud formation from the parent organism. After growing to full size, the bud gets detached and form a new independent individual.

(f) Vegetative reproduction : When vegetative part of a plant like stems, leaves and root etc. give rise to new ones, it is called vegetative reproduction.

Question 2.
What is vegetative reproduction ? Describe vegetative reproduction in different parts of the plant.
Answer:
Vegetative reproduction means growing of off springs from the vegetative parts of the plant like roots, stems, and leaves.
(i) Vegetative propagation by roots : Thick roots of sweet potato, dahlia or asparagus give rise to new ones, inside the soil only.

(ii) Vegetative propagation by stems : In certain plants like potato, ginger, sugarcane etc, new plants grow from the stems of these plants. In potatoes these are small ‘eyes’ on the swollen stem. These eyes germinate to give rise to new plants. Ginger and turmeric also give rise to new plants rom the small buds growing on their swollen stems.

(iii) Vegetative reproduction by leaves : In plants like Bryophyllum Small plantlets grow from the margins of the leaves. These plantlets when detached from the leaf and grown develops into an independent plant.

Question 3.
Explain Sexual Reproduction in plants.
Answer:
Sexual reproduction occurs in plants having well developed reproductive parts in them. Flowers are the reproductive parts of the plant. Flowers can be unisexual i.e. having only male or female reproductive parts, and Bisexual i.e. having both male and female reproductive parts.

Female reproductive part of the flower i.e. the pistil form female ovules and male reproductive parts i.e. Androecium give rise to male gametes. When male and female gametes fuse in the ovary of the flower the process of fertilisation takes place. Male gametes are carried to the female flowers far away by agents like wind, water, insects and animals. This is called pollination. After fertilization the ovary of the flower becomes pulpy and juicy to form fruits. The ovules become the seeds.

Reproduction in Plants Class 7 HBSE Notes

• Reproduction is the process by which all the living organisms produce more of their own kind.
• The reproduction in plants occur by two methods : asexual reproduction and sexual reproduction.
• Asexual reproduction is reproduction without seeds involving only single parent.
• Asexual reproduction occurs in lower forms of the plants.
• Various methods of asexual reproduction are : Binary fission, fragmentation, Endospore formation, spore formation, Budding and vegetative reproduction.
• Binary fission is division of elongated parent cell into two daughter cell. It mostly occurs in bacteria. Some bacteria reproduce by endospore formation.
• Fragmentation is splitting up of filaments of algae in two or more than two parts, which develop into complete organism.
• Spores are formed in fungi, spores along with outer hard covering are called sporangium. Sporangium burst to release spores.
• Bud is a small bulb like projection, which comes out of yeast cell. It grows and detach from the parent cell to form a new yeast cell.
• Vegetative propagation is the birth of new ones from the vegatative parts of the plant like leaves, roots, stems etc.
• Sexual reproduction is the reproduction by seeds involving both male and female plants.
• Male and female gametes fuse to form zygote which grows into a developed new plant.
• Ovaries of the plant develop into fruit after fertilization and ovules becomes seeds.
• Male pollen grains are transferred from one flower to another and this is called pollination.
• When pollen grain of same flower are transferred from anther to stigma of same flower, it is called self-pollination.
• When pollens of a flower are transferred to stigma of another flower of same kind, it is called cross-pollination.

Haryana State Board HBSE 7th Class Science Solutions Chapter 13 Motion and Time Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 13 Motion and Time

HBSE 7th Class Science Motion and Time Textbook Questions and Answers

Question 1.
Classify the following as motion along a straight line, circular or oscillatory motion :
(i) Motion of your hands while running.
(ii) Motion of a horse pulling a cart on a straight road.
(iii) Motion of a child in a merry go round.
(iv) Motion of a child on a see-saw.
(v) Motion of the hammer of an electric bed.
(vi) Motion of a train on a straight bridge.
Answer:
(i) Oscillatory
(ii) along a straight, line
(iii) circular
(iv) oscillatory
(v) oscillatory
(vi) along a straight line.

Question 2.
Which of the following is not correct?
(i) The basic unit of time is second.
(ii) Every object moves with a constant speed.
(iii) Distance between two cities are measured in kilometres.
(iv) The time period of a given pendulum is not constant.
(v) The speed of a train is expressed in m/h.
Answer:
(ii), (iv) (v).

Question 3.
A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?
Answer:
Time period of a pendulum is time taken to complete 1 oscillation
Time taken to complete = 32 s.
20 oscillations
Time taken to complete = \(\frac { 32 }{ 20 }\)s.
1 oscillation
= 1.6 s.
∴ Time period of pendulum is 1.6 seconds.

Question 4.
The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.
Answer:
Distance = 240 km.
Time taken = 4 hr.
Speed = \(\frac { Distance covered }{time taken }\)
= \(\frac { 240 }{ 4 }\) \(\frac { km }{ h }\)
= 60 km/h.
Speed of the train is 60 km/h.

Question 5.
The odometer of a car reads 57321.0 km when the clock shows the time 08:30 AM. What is the distance moved by the car, if at 08:50 AM, the odometer reading has changed to 57336.0 km? Calculate the speed of the car in km/min during this time. Express the speed in km/ h also.
Answer:
Distance = 57336.0 km – 57321 km = 15 Km
Time = 8.50 Am. – 8.30 Aim. = 20 min
Speed = \(\frac { Distance }{ time }\) = \(\frac { 15 }{ 20 }\) km/m
= 0.75 km/m. = 45 km/h

Question 6.
Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s. Calculate the distance between her house and’the school.
Answer:
Time taken = 15 min
Speed = 2 m/s.
Distance = Speed x time
= 15 x 2
= 30 m.
So, distance between Salma’s School and her house is 30 metre.

Question 7.
Show the shape of the distance-time graph for the motion in the following cases :
(i) A car moving with a constant speed.
(ii) A car parked on a side road.
Answer:

Question 8.
Which of the following relations is correct?
(i) Speed = Distance x Time
(ii) Speed = \(\frac { Distance }{ Time }\)
(iii) Speed = \(\frac { Time }{ Distance }\)
(iv) Speed = \(\frac { 1 }{ Distance x Time }\)
Answer:
(ii) Speed = \(\frac { Distance }{ Time }\) is correct.

Question 9.
The basic unit of speed is :
(i) km/min
(ii) m/min
(iii) km/h
(iv) m/s
Answer:
(iv) m/s

Question 10.
A car moves with a speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. The total distance covered by the car is :
(i) 100 km
(ii) 25 km
(iii) 15 km
(iv) 10 km
Answer:
(ii) 25 km

Question 11.
Suppose, the two photographs shown in Fig. 13.1 and Fig. 13.2, had been taken at an interval of 10 seconds. If a distance of 100 metres is shown by 1 cm in these photographs. Calculate the speed of the blue car.
Answer:
0.1 cm/s or 10 m/s.

Question 12.
Fig. 13.16 shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?

Answer:
‘A’ car is moving faster.

Question 13.
Which of the following distance-time graphs shows a truck moving with speed which is not constant?

Answer:

Extend Learning – Activities and Projects

Question 1.
You can make your own sundial and use it to mark the time of the day at your place. First of all find the latitude of your city with the help of an atlas. Cut out a triangular piece of a cardboard such that its one angle is equal to the latitude of your place and the angle opposite to it is a right angle. Fix this piece, called gnomon, vertically along a diameter of a circular board a shown in Fig. 13.4. One way to fix the gnomon could be to make a groove along a diameter on the circular board.

Next, select an open space, which receives sunlight for most of the day, Mark a line on the ground along the North-South direction. Place the sundial in the sun as shown in Fig. 13.4 Mark the position of the tip of the shadow of the gnomon on the circular board as early in the day as possible, say 8:00 AM. Mark the position of the tip of the shadow every hour throughout the day. Draw lines to connect each point marked by you with the centre of the base of the gnomon as shown in Fig. 13.4. Extend the lines on the circular board up to its periphery. You can use „ this sundial to read the time of the day at your place. Remember that the gnomon should always be placed in the North- South direction as shown in Fig. 13.4.

Answer:
Do it yourself.

Question 2.
Collect information about time-measuring devices that were used in the ancientitimes in different partrs of the world. Prepare a brief write up on each one of them. The write up may include the name of the device, the place of its origin, the period when it was used, the unit in which the time was measured by it and a drawing or a photograph of the device, if available.
Answer:
Do it yourself

Question 3.
Make a model of a sand clock which can measure a time interval of 2 minutes (Fig. 13.5).

Answer:
Do it yourself

Question 4.
You can perform an interesting activity when you visit a park to ride a swing. You will require a watch. Make the swing oscillate without anyone sitting on it. Find its time period in the same way as you did for the pendulum. Make sure that there are no jerks in the motion of the swing. Ask one of your friends to sit on the swing. Push it once and let it swing naturally. Again measure its time period. Repeat the activity with different persons sitting on the swing. Compare the time period of the swing measured in different cases. What conclusions do you draw from this activity?
Answer:
Do it yourself.

HBSE 7th Class Science Motion and Time Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is motion?
Answer:
Motion is the change in the position of a body with respect to time and its surroundings.

Question 2.
What is uniform motion?
Answer:
When a body covers equal distance in equal intervals of time, the motion is called uniform motion.

Question 3.
What is speed?
Answer:
Speed is the distance covered by a body in a unit time.

Question 4.
Write one way in which people used to measure time in early days?
Answer:
People used to measure time with the help of Sundials.

Question 5.
What is the use of stop-watch?
Answer:
Stop-watch is used to measure exact time in case of athletic events as it can be stopped and started any moment.

Question 6.
What is a pendulum?
Answer:
A pendulum is a small non-magnetic ball like body, suspended by a light string.

Question 7.
What is a uniform motion?
Answer:
Motion of a body along a straight line covering equal distances in equal intervals of time is called a uniform motion.

Question 8.
What are the units of measuring speed?
Answer:
Speed is measured in metre per second (m/s) or kilometre per hour (km/h).

Short Answer Type Questions

Question 1.
Distinguish between uniform and non-uniform motion.
Answer:
Uniform motion is the equal distances covered in equal intervals of time. It means body moves with a constant speed. Non-uniform motion is the unequal distances covered in equal intervals of time. It means the body moves with unconstant speed.

Question 2.
How can we make a pendulum of our own? What is the time period of a pendulum?
Answer:
We can make a pendulum by susptending a metal ball with a cotton thread. The other end of the thread can be tied to some support. The time taken by a pendulum to complete its to and fro movement i.e. one oscillation is called the time period of the pendulum.

Question 3.
How can we determine the motion made by any body to be uniform or non-uniform with the help of a distance – time graph?
Answer:
If the distance – time graph obtained shows a straight line, the motion of the body is said to be uniform and if we obtain a curved line on a distance time graph that means the body is undertaking non-uniform motion. Thus a distance time graph helps in determining the uniform or non-uniform speed of the body.

Question 4.
A train is running at a speed of 50 km/h. How long will it take to cover a distance of 250 km.?
Answer:
Speed = 50 km/h
Distance = 250 km.
Time = ?
S = \(\frac { d }{ t }\)
50 = \(\frac { 250 }{ t }\)
∴ t = \(\frac { 250 }{ 50 }\) hr = 5 hr.

Question 5.
Shatabdi Express takes 6 hours to reach Lucknow, at a speed of 60 km/h. Find the distance it travels.
Answer:
Time = 6 hr.
Speed = 60 km/h
Distance = Speed x time
= 60 x 6 = 360 km
∴ Shatabdi travels 360 km at a speed of 60 km/h in 6 hr.

Question 6.
A car travels a distance of 200 km at the speed of 50 km/h. Calculate the time taken to cover the distance.
Answer:
Distance = 200 km
Speed = 50 km/h
Time = \(\frac { Distance }{ Speed }\) = \(\frac { 200 }{ 50 }\) = 4h
Car will take 4 h to cover the distance.

Long Answer Type Questions

Question 1.
Given below is a table showing time taken by a car to travel various distances. What do you infer from this data?

Answer:
We see that the car covers the distance of first 10 m in 1 sec. It again covers the distance of 10 m in another time of 1 sec i.e. 2-1 = 1 sec. So, we find that the car covers every 10 m in each 1 sec. It means that the car is covering equal distance in equal interval of time. When a body covers equal distance in equal intervals of time, it is said to be in a uniform motion. So, this data shows that the car is moving with a constant speed.

Question 2.
Describe various methods used to measure time in earlier times?
Answer:
There were no electronic watches in earlier times. Measuring time was a little bid difficult. The earliest method of measuring time was based on the position of the Sun. The Sundials were used for this purpose. Time was measured by the shadow casted by the changing position of the Sun from day to night. Chinese made a water clock 6000 years ago. Sand Clock was also used to measure time. Sand Clock was used by Romans. The time taken by sand to fall into the lower chamber from the upper chamber was considered to be the unit of measuring time. The discovery of pendulum helped in determining the exact time before the electronic watches were invented.

Question 3.
What is a pendulum? How does it help in determing time?
Answer:
Pendulum is a simple device which shows periodic motion. A simple pendulum consists of a non-magnetic metal ball called bob. This bob is suspended with help of a string. The open end of the string is tied to a support. Bob of the pendulum is held at a side and released. It starts moving in a to and fro motion. This is called an oscillatory motion. The time taken by the pendulum to complete one oscillation is called time period. This time period is always same with a pendulum having same length. Time period changes with the change in the length of the string. The string of the pendulum is adjusted to the length, that it completes one oscillation in second and it keeps on moving the clock giving us time.

Motion and Time Class 7 HBSE Notes

• Motion is the change in the position of an object with respect to its surroundings.
• Motion can be of many types. It can be along a straight line, circular, oscillatory.
• Motion can be uniform or non-uniform motion.
• Uniform motion means equal distance covered in equal intervals of time. It means a constant motion.
• Non-uniform motion means unequal distance covered in equal intervals of time.
• Distance moved by an object in unit time is called its speed.
• Basic unit of measuring speed is (m/s) meter / second.
• Time is measured in respect to the periodic motions.
• Pendulum was the first device to measure time exactly.
• In earlier days time Was measured by various objects like sundials, sand clocks, water clocks, etc.
• With the discovery of pendulum, devices to measure exact time were invented.
• Now-a-days various devices like stop-watch and other electronic devices are used to measure time intervals smaller than even a second.
• Distance time graph gives us an idea about the motion of the object. Straight-line obtained on this graph depicts constant motion, while non-constant motion is depicted by various shapes on the graph.

Haryana State Board HBSE 7th Class Science Solutions Chapter 14 Electric Current and its Effects Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 14 Electric Current and its Effects

HBSE 7th Class Science Electric Current and its Effects Textbook Questions and Answers

Question 1.
Draw in your notebook the symbols to represent the following components of electrical circuits: Connecting wires, Switch in the ‘OFF’ position. Bulb, Cell, Switch in the ‘ON’ position, and Battery.
Answer:
Draw in your notebook the symbols to represent the following components of electrical circuits :
Connecting wires — —
Switch in off position — —
Bulb — —
Cell — —
Switch in ‘on’ position — —
Battery — —

Question 2.
Draw the circuit diagram to represent the circuit shown in Fig. 14.1.
Answer:

Question 3.
Fig 14.2 shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.
Answer:

Question 4.
The bulb in the circuit shown in Fig 14.3 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulbs glow.
Answer:
The problem in this circuit is that of the battery. The cells have not been arranged in right series. The correct circuit is like this.

Question 5.
Name any two effects of electric current.
Answer:
Electric current has following effects:

• Electric current can give rise to heating and lighting.
• Electric current can make a straight conductor a temporary magnet.

Question 6.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
Answer:
When current is passed through the wire, it deflects the compass near it from its north-south position behaving like a magnet. This is called magnetic effect of the current. As we know that needle of the compass is made up of a thin magnet, when this needle comes in contact with another magnet the like poles of the magnet repell each other and opposite poles attract each other. So the deflection is seen in the needle. In this case the wire behaves like a magnet and cause deflection in needle of the compass.

Question 7.
Will the compass needle show deflection when the switch in the circuit shown by Fig. 14.4 is closed?

Answer:
No, because there is no source of electric current in this circuit i.e. there is no battery.

Question 8.
Fill in the blanks:
(a) Longer line in the symbol for a cell represents its _______ terminal.
(b) The combination of two or more cells is called a _______.
(c) When current is switched on in a room-heater, its _______.
(d) The safety device based on the heating effect of electric current is called a _______.
Answer:
(a) Positive
(b) Battery
(c) Element becomes red hot and emit heat
(d) Fuse.

Question 9.
Mark ‘T’ if the statement true and ‘F’ if it is false.
(a) To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell.
(b) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks.
(c) An electromagnet does not attract a piece of iron.
(d) An electric bell has an electromagnet.
Answer:
(a) F
(b) T
(c) F
(d) T

Question 10.
Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
Answer:
No, the plastic bags do not get attracted by the magnet, so they cannot be separated by an electromagnet. Plastic bags are not magnetic materials, only magnetic materials like iron can be attracted by the magnet.

Question 11.
An electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of a wire. Would you agree? Give reasons for your response.
Answer:
No, we would not agree to allow to replace the fuse by a wire. Wires in the fuses are of specific metting points. So we should always use ISI marked fuses in our houses to save short circuits.

Question 12.
Zubeda made an electric circuit using a cell holder shown in Fig. 14.4, a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
Answer:
It is important to put the cells in right series. The positive terminal of the cell should be connected with negative terminal of the second cell. The switch should be closed properly and bulb should not be fused. If Zubeda will check these then the bulb will certainly glow.

Question 13.
In the circuit shown in Fig. 14.5
(i) Would any of the bulb glow when the switch is in the ‘OFF’ position?
(ii) What will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?

Answer:
(i) No, bulb will glow.

(ii) The bulb A will glow first, follow by B bulb and then C, because A bulb comes first in the path of electric current flowing from positive terminal towards the negative terminal of the battery.

Extended Learning-Activities and Projects

Question 1.
Set up the circuit shown in Fig. 14.6 again. Move the key to ‘ON’ position and watch carefully in which direction the compass needle gets deflected. Switch ‘OFF’ the current. Now keeping rest of the circuit intact, reverse the connections at the terminal of the cell. Again switch ‘on’ the current. Note the direction in which the needle gets deflected. Think of an explanation.
Answer:
Do it yourself.

Question 2.
Make four electromagnets with 20, 40, 60 and 80 turns. Connect them one by one to a battery of 2 cells. Bring the electromagnet near a box of pins. Count the number of pins attracted by it. Compare the strengths of the electromagnets.
Answer:
Do it yourself.

HBSE 7th Class Science Electric Current and its Effects Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is electric current?
Answer:
Flow of electrons is called electric current.

Question 2.
What is conventaional current?
Answer:
The current flowing the positive end of the conducting wire towards the negative end is called conventaional current.

Question 3.
What are the different sources of current in an electric circuit?
Answer:
Cell or a battery are the sources of elctric current in an electric circuit.

Question 4.
What role does a switch plays in an electric circuit?
Answer:
The switch regulates the flow of electric current. It allows the current to pass when it is in ‘ON’ position.

Question 5.
Write the symbols of the following : Switch (open).
Switch closed and a cell.
Answer:

Question 6.
What is an open electric circuit?
Answer:
An electric circuit having the switch in ‘off position is called open electric circuit.

Question 7.
What is a closed electric circuit?
Answer:
An electric circuit having the switch in ‘on’ position is called a closed circuit or a complete circuit.

Question 8.
Which effect of the electric current enables the room heater to heat the room?
Answer:
The heating and lighting effect of the electric current enables the room heater to heat the room.

Question 9.
What is a fuse?
Answer:
It is a safety device used to avoid damages from short circuits and over loading in electric appliances.

Question 10.
Which effect of the electric current is used in Electric bells?
Answer:
The magnetic effect of the electric current is used in electric bells to make the sound.

Short Answer Type Questions

Question 1.
What is an electric current and electric circuit?
Answer:
Flow of electrons is called electric current. The path through which the electric current passes is called an electric circuit.

Question 2.
What are the components of the electric circuit? Name different components of the electric circuit and draw their symbols.
Answer:
Various elelments connected in the electric circuit are called components of the electric circuit. Following are some components of electric circuit and their symbols :

Question 3.
What is a cell and what is a battery?
Answer:
Cell and battery are both the sources of electric current in an electric circuit. A cell has two terminals – +ve terminal and – ve terminal. A combination of two or more than two cells is called a battery. Battery is formed by joining a positive terminal of a cell to the negative terminal of other cell.

Question 4.
What is an electric fuse? Explain its working.
Answer:
A fuse is a safety device used in household circuit to prevent damage to electric appliances due to overload and short circuit. It is the weakest part in the electric circuit. It melts and breaks the circuits when the problem arises in the circuit due to short circuiting, overloading or fluctuations of current in power supply system.

Question 5.
What is short circuit and overloaded circuit?
Answer:
Short circuit occurs when live wire and neutral wire come in direct contact. The short circuit occurs either due to melting of plastic insulation or connection of live wire with the earth wire. An overload circuit is the one through which more current passes than it can bear.

Question 6.
What is an M. C. B.?
Answer:
M.C.B. is miniature circuit breaker. This is a safety device like a fuse. It is used instead of or in addition to fuses, in household circuits. It is a switch that automatically switches off a current when it exceeds the specified maximum limit.

Question 7.
Write any three applications of the electromagnets.
Answer:
Fallowing are the applications of the electromagnets :

• Electromagnets are used to separate scrap iron from other metallic scraps.
• Used in electric motors of washing machines, fans, air conditioners etc.
• Used for preparing strong magnets.

Long Answer Type Questions

Question 1.
Explain the construction and working of an electric bell with help of a labelled diagram.
Answer:
An electric bell consists of an electromagnet, Armature, contact spring, Hammer and gong.
Electromagnet: It consists of a U-shaped soft iron rod having insulated copper wire wounded on it. One end of wire is connected to terminal T and other to the brass stud.

Armature: is a soft iron rod, suspended to brass stud. It faces the poles of the electromagnet.

Contact spring is attached to the armature and to a silver-cadmium alloy contact point. Spring is made up of steel.

Contact screw adjustment: It is a brass pillar having a brass screw passing through it. The tip of the screw is made up of silver cadmium alloy. Pillar is connected to T₂ with a copper wire.

Hammer and Gong : Hammer is made up of steel and is attached to the armature. Gong is made up of brass, and the hammer strikes the gong to make the sound.

Working : When electric current passes through T₁ and T₂, current passes from the battery to electromagnet, then to the contact screw and to T₂ completing the circuit. Electromagnet pulls the armature towards itself, the contact spring gets under tension, hammer strikes against gong thus making the sound. The whole process stops, when current stops flowing.

Electric Current and its Effects Class 7 HBSE Notes

• Flow of electrons is called electric current.
• The path in which the electric current flows is called an electric circuit.
• Conventially the current is said to flow from positive end of the conducting wire to the negative end of the conducting wire.
• There are many components which are attached to the path of the electric current. These are called the elements of the electric circuit,
• Elements like cell, battery, switch, bulb, connecting wires are represented by different symbols.
• Cell and battery are the sources of the electric current in a circuit. Battery is the combination of two or more than two cells.
• A circuit is said to be complete or closed when the switch regulating the flow of the current is in ‘on’ position when the switch is in ‘off’ position the circuit is called open.
• Flow of the electric current causes certain effects like heating and lighting and electromagnetism.
• The electric appliances like room heaters, gysers, rods etc. give out heat due to heating effect.
• When electric current passes through a magnetic substance like iron, it behaves like a temporary magnet.
• Electric bell works on this principle.
• Hans Christian Oersted found out the relation between electricity and magnetism.
• A fuse is a safety device used in the household circuits to prevent damage to electric appliances due to overload or short circuits.

Haryana State Board HBSE 7th Class Science Solutions Chapter 15 Light Textbook Exercise Questions and Answers.

Haryana Board 7th Class Science Solutions Chapter 15 Light

HBSE 7th Class Science Light Textbook Questions and Answers

Question 1.
Fill in the blanks :
(a) An image that cannot be obtained on a screen is called _________.
(b) Image formed by a convex _________ is always virtual and smaller in size.
(c) An image formed by a _________ mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a _________ image.
(e) An image formed by a concave _________ cannot be obtained on a screen.
Answer:
(a) virtual image
(b) mirror
(c) plane
(d) real
(e) lens.

Question 2.
Mark ‘T’ if the statement is true and ‘F’ if it is false :
(a) We can obtain an enlarged and erect image by a convex mirror.
(b) A concave lens always form a virtual image.
(c) We can obtain a real, enlarged and inverted image by a concave mirror.
(d) A real image cannot be obtained on a screen.
(e) A concave mirror always form a real image.
Answer:
(a) F
(b) T
(c) T
(d) F
(e) F

Question 3.
Match the items given in Column I with one Or more items of Column II.

Answer:
(a) (v)
(b) (ii)
(c) (i)
(d) (iii)
(e) (vi)

Question 4.
State the characteristics of the image formed by a plane mirror.
Answer:

• Plane mirror forms an erect image.
• It forms a virtual image.
• Size of the image is same as that of the object.
• Image gets formed at the same distance behind the mirror as the object stands infornt of it.
• Image formed is a laterally inverted image, i.e. right hand side of the object seems to be the left hand side and vice-versa.

Question 5.
Find out the letters of English alphabet or any other language known to you in which the image formed in a place mirror appears exactly like the letter itself. Discuss your findings.
Answer:
Letters like A, H, I, M, O, T, U, V, W etc appear same when seen through a plane mirror.

Question 6.
What is a virtual image? Give one situation where a virtual image is formed.
Answer:
The image which cannot be taken on a screen is called a virtual image. When some object is placed very close to the concave mirror we do not get any image of that object on the white screen placed behind the mirror. Such image is called a virtual image.

Question 7.
State two differences between a convex and a concave lens.
Answer:

Question 8.
Give one use each of a concave and a convex mirror.
Answer:

• Use of Concave mirror: Concave mirror is used by dentists to- examine the teeth.
• Use of Convex mirror: Convex mirror is used as side view mirror in vehicles.

Question 9.
Which type of mirror can form a real image?
Answer:
Concave mirror can form a real image.

Question 10.
Which type of lens forms always a virtual image?
Answer:
Convex lens always form a virtual image.

Choose the correct option in questions 11-13

Question 11.
A virtual image larger than the object can be produced by a _________.
(i) concave lens
(ii) concave mirror
(iii) convex mirror
(iv) plane mirror
Answer:
(iii) convex mirror

Question 12.
David is observing his image in a plane mirror. The distance between the mirror and his image is 4 m. If he moves 1 m towards the mirror, then the distance between David and his image will be _________.
(i) 3 m
(ii) 5 m
(iii) 6 m
(iv) 8 m
Answer:
(i) 3 m

Question 13.
The rear view mirror of a car is a plane mirror. A driver is reversing his car at a speed of 2 m/s. The driver sees in his rear view mirror the image of a truck parked behind his car. The speed at which the image of the truck appears to approach the driver will be _________.
(i) 1m/s
(ii) 2m/s
(iii) 4mls
(iv) 8m/s
Answer:
(iii) 4mls

Extended Learning-Activities and Projects

Question 1.
Play with a mirror Write your name with a sketch pen on a thin sheet of paper, polythene or glass.

Read your name on the sheet while standing in front of a plane mirror. Now look at your image in the mirror.
Answer:
Do it yourself.

Question 2.
A burning candle in water
Take a shoe box, open on one side. Place a small lighted candle in it. Place a clear glass sheet (roughly 25 cm x 25 cm) infront of this candle (fig. 15.1). Try to locate the image of the candle behind the glass sheet. Place a glass of water as its position. Ask your friends to look at the image of the candle through the sheet of glass. Ensure that candle is not visible to your friends. Your friends will be surprised to see the candle burning in water. Try to explain the reason.
Answer:
Do it yourself.

Question 3.
Make a rainbow’.
Try to make your own rainbow. You can try this project in the morning of in the evening. Stand with your back towards the sun. Take a hosepipe or a water pipe used in the garden. Make a find spray in front of you. Your can see different colours of rainbow in the spray.
Answer:
Do it yourself.

Question 4.
Visit a laughing gallery in some science centre or a science park or a village mela. You will find some large mirrors there. You can see your distorted and funny images in these mirrors. Try to find out the kind of mirrors used there.
Answer:
Do it yourself.

Question 5.
Visit a nearby hospital. You can also visit the clinic of an ENT specialist, or a dentist. Request the doctor to show you the mirrors used for examining ear, nose,
throat and teeth. Can you recognise the kind of mirror used in these instruments?
Answer:
Do it yourseld.

Question 6.
Role play
Here is a game that a group of children can play. One child will be chosen to act as object and another will act as the image of the object. The object and the image will sit opposite to each other. The object will make movements, such as raising a hand, touching an ear, etc. The image will have to make the correct movement following the movement of the object. The rest of the group will watch the movements of the image. If the image fails to make the correct movement, she/he will be retired. Another child will take her/his place and the game will continue. A scoring scheme can be introduced. The group that scores the maximum will be declared the winner.
Answer:
Do it yourself.

HBSE 7th Class Science Light Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What do you mean by rectilinear propagation of light?
Answer:
Rectilinear propagation of light means that beam of a light always travels in a straight line.

Question 2.
How can we change the direction of the light?
Answer:
We can change the direction of the light by the phenomenon called reflection.

Question 3.
What do you mean by reflection of light?
Answer:
When a ray of light falls on the surface of any mirror, it bounces back in the same medium. This is called reflection of light.

Question 4.
What is a mirror?
Answer:
Any polished or shining surface is called a mirror.

Question 5.
What do you mean by a real image?
Answer:
Image which can be obtained on a screen is called a real image.

Question 6.
What do you mean by a virtual image?
Answer:
Image which cannot be obtained on a screen is called a virtual image.

Question 7.
What is a convex mirror?
Answer:
A mirror which reflects the light from its inner polished side.

Question 8.
What is a concave mirror?
Answer:
A mirror, which reflects light from its outer polished surface.

Question 9.
What kind of image is formed by a plane mirror?
Answer:
It forms an erect, virtual and image of same size as that of the object.

Question 10.
What kind of image is formed by a concave mirror?
Answer:
It can form both real and virtual, erect or inverted image.

Question 11.
What kind of image is formed when an object is placed very close to the concave mirror?
Answer:
A virtual erect and a magnified image will be formed.

Question 12.
What kind of image is formed by a convex mirror?
Answer:
Convex mirror forms an erect, virtual and diminished image.

Question 13.
What kind of image is formed by a concave lens?
Answer:
An erect, virtual and diminished image is formed by a concave lens.

Question 14.
What happens when a beam of light enters a prism?
Answer:
The beam of light splits into seven colours.

Question 15.
What do you mean by lateral inversion?
Answer:
When right hand side of an object appears as the left hand side and vice-versa.

Short Answer Type Questions

Question 1.
What is a virtual image? Give one example of virtual image.
Answer:
Virtual image : It is an image which cannot be obtained on a screen. It is formed when the reflected rays appears to meet each other but actually do not meet in reality. It is always erect. Image formed by a plane mirror is a virtual image.

Question 2.
What is real image of an object?
Answer:
Real image is formed when two or more reflected rays actually meet. This image can be obtained on a screen. It is always inverted. Pin-hole camera forms a real image.

Question 3.
Give two uses of concave mirror.
Answer:

• It is used as a reflector in search-light and head-lights of the automobiles.
• It is used as a shaving mirror.

Question 4.
Give two uses of convex mirror.
Answer:

• It is used in the cars and scooters to get the rear view to see the traffic coming from behind.
• It is used as reflectors in street lamps so as to diverse the light over a large area.

Question 5.
What do you mean by reflection of light?
Answer:
When a beam of light is incident on a plane surface a part of it is scattered back into the same medium. The scattering back of light into the same medium is called reflection.

Question 6.
Why is silvered glass used as a mirror?
Answer:
The silvered glass has a smooth surface and the smoothness helps in forming a clear image. Silvering makes it shiny and the shiny surface helps in reducing the absorption.

Question 7.
A man walks towards a plane mirror. At what rate will his image move if :
(a) the mirror is stationary,
(b) the mirror moves towards the man.
Answer:
(a) If the mirror is stationary the image moves at the same rate as the man.
(b) When the mirror moves towards the man the image moves at twice the rate of the mirror.

Question 8.
State four characteristics of the image formed by a plane mirror.
Answer:

• The image formed is as far behind the mirror as the object.
• It is exactly of same shape and size.
• It is erect but laterally inverted.
• It is virtual.

Question 9.
Distinguish between a real image and a virtual image.
Answer:
Difference between a real and virtual image :

Question 10.
Distinguish between a concave mirror and convex mirror.
Answer:

Long Answer Type Questions

Question 1.
How would you ascertain that a given mirror is a (a) Plane mirror, (b) Concave mirror, (c) Convex mirror without touching their surface?
Answer:
Hold the given mirror in the hand near your face, see the image. If the image is upright of the same size and does not change in size by moving the mirror, then the mirror is a plane mirror.

It the image is upright, larger and becomes inverted on moving the mirror away from your face, then the given mirror is a concave mirror. If the image is upright, smaller than your face and remains upright on moving the mirror away from your face, then the given mirror is the convex mirror. In this way one can ascertain the kind of mirror, without touching its surface.

Light Class 7 HBSE Notes

1. Light is an invisible energy which casue the sensation of sight.

2. Any object that gives out light is called the source of light e.g. Sun, firefly, candle etc.

3. Sun, moon, stars etc are called natural sources of light.

4. Candle, bulb etc are called man-made sources of light.

5. Light always travels in a straight line, this property of light is called the rectilinear propagation of light.

6. When light falls on a plane mirror, it falls back. This property of turning back of light is called in the same medium is called reflection of light.

7. There are two laws of reflection :
(i) The incident ray the normal at the point of incidence and the reflected ray lie in the same plane.
(ii) The angle of reflection is equal to the angle of incidence.

8. Any polished and shining surface is called a mirror.

9. Mirrors are of two types : concave mirror and convex mirror.

10. Concave mirror form a real and inverted image of the object.

11. Convex mirror always forms a virtual erect and small image.

12. Real image is one which can be obtained on a screen.

13. Virtual image is one, which cannot be obtained on a screen.

14. Lenses are also used to form images. Lenses are used to make spectacles, microscopes, magnifying glasses and telescopes etc.

15. Lenses are of two types. Concave lens and convex lens.

16. Concave lens is also called diverging lens, because it diverge the light falling on it. Convex lens is called the converging lens because it converges the light falling on it.

17. Concave lens forms, virtual erect and diminished image.

18. Convex lens can form both real and virtual images depending upon the position of the object. It magnifies the objects, when they are placed very near the lens.

19. White light splits into seven colours when it enters a prism.

20. This phenomenon is called dispersion of light.