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
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.
(a) virtual image
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.
Match the items given in Column I with one Or more items of Column II.
|Column I||Column II|
|(a) A plane mirror||(i) Used as a magnifying glass.|
|(b) A convex mirror||(ii) Can form image of objects spread over a large area.|
|(c) A convex lens||(iii) Used by dentists to see enlarged image.|
|(d) A concave mirror||(iv) The image is always inverted and magnified.|
|(e) A Concave lens||(v) The image is erect and of the same size as the object.|
|(vi) The image is erect and smaller in size than the object.|
State the characteristics of the image formed by a plane mirror.
- 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.
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.
Letters like A, H, I, M, O, T, U, V, W etc appear same when seen through a plane mirror.
What is a virtual image? Give one situation where a virtual image is formed.
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.
State two differences between a convex and a concave lens.
|Convex lens||Concave lens|
|(i) Convex lens can form both real and virtual images.||(i) Concave lens always form a virtual image.|
|(ii) It can form magnified image.||(ii) Image is always diminished in size.|
Give one use each of a concave and a convex mirror.
- 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.
Which type of mirror can form a real image?
Concave mirror can form a real image.
Which type of lens forms always a virtual image?
Convex lens always form a virtual image.
Choose the correct option in questions 11-13
A virtual image larger than the object can be produced by a _________.
(i) concave lens
(ii) concave mirror
(iii) convex mirror
(iv) plane mirror
(iii) convex mirror
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
(i) 3 m
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 _________.
Extended Learning-Activities and Projects
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.
Do it yourself.
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.
Do it yourself.
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.
Do it yourself.
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.
Do it yourself.
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?
Do it yourseld.
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.
Do it yourself.
HBSE 7th Class Science Light Important Questions and Answers
Very Short Answer Type Questions
What do you mean by rectilinear propagation of light?
Rectilinear propagation of light means that beam of a light always travels in a straight line.
How can we change the direction of the light?
We can change the direction of the light by the phenomenon called reflection.
What do you mean by reflection of light?
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.
What is a mirror?
Any polished or shining surface is called a mirror.
What do you mean by a real image?
Image which can be obtained on a screen is called a real image.
What do you mean by a virtual image?
Image which cannot be obtained on a screen is called a virtual image.
What is a convex mirror?
A mirror which reflects the light from its inner polished side.
What is a concave mirror?
A mirror, which reflects light from its outer polished surface.
What kind of image is formed by a plane mirror?
It forms an erect, virtual and image of same size as that of the object.
What kind of image is formed by a concave mirror?
It can form both real and virtual, erect or inverted image.
What kind of image is formed when an object is placed very close to the concave mirror?
A virtual erect and a magnified image will be formed.
What kind of image is formed by a convex mirror?
Convex mirror forms an erect, virtual and diminished image.
What kind of image is formed by a concave lens?
An erect, virtual and diminished image is formed by a concave lens.
What happens when a beam of light enters a prism?
The beam of light splits into seven colours.
What do you mean by lateral inversion?
When right hand side of an object appears as the left hand side and vice-versa.
Short Answer Type Questions
What is a virtual image? Give one example of virtual image.
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.
What is real image of an object?
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.
Give two uses of concave mirror.
- It is used as a reflector in search-light and head-lights of the automobiles.
- It is used as a shaving mirror.
Give two uses of convex mirror.
- 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.
What do you mean by reflection of light?
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.
Why is silvered glass used as a mirror?
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.
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.
(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.
State four characteristics of the image formed by a plane mirror.
- 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.
Distinguish between a real image and a virtual image.
Difference between a real and virtual image :
|Real Image||Virtual Image|
|1. It is formed by actual intersection of rays.||1. It is formed when rays appear to intersect.|
|2. It can be taken on a screen.||2. It cannot be taken on a screen.|
|3. It is always inverted.||3. It is always erect.|
Distinguish between a concave mirror and convex mirror.
|1. It reflects light from its inner shining surface.||1. It reflects light from its outer shining surface.|
|2. It can form both real and virtual image.||2. It always forms a virtual image.|
|3. It can form both erect and inverted image.||3. It always forms an erect image.|
|4. It can form a magnified image.||4. It always forms a diminished image.|
Long Answer Type Questions
How would you ascertain that a given mirror is a (a) Plane mirror, (b) Concave mirror, (c) Convex mirror without touching their surface?
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.