NCERT Solutions Class 7 Science Chapter 15 Light
1. Fill in the blanks.
(a) An image that cannot be obtained on a screen is called a ____________.
(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) An image that cannot be obtained on a screen is called a virtual image.
(b) Image formed by a convex mirror is always virtual and smaller in size.
(c) An image formed by a plane 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 real image.
(e) An image formed by a concave lens cannot be obtained on a screen.
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 forms a real image.
Answer:
a) False
b) True
c) True
d) False
e) False
3. Match the items given in Column I with one or more items in Column II.
| Column-I |
Column-II |
| (a) A plane mirror |
(i) Used as a magnifying glass. |
| (b) A convex mirror |
(ii) Can form images of objects spread over a large area. |
| (c) A convex lens |
(iii) Used by dentists to see an enlarged image of teeth. |
| (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. |
Answer:
| Column-I |
Column-II |
| (a) A plane mirror |
(v) The image is erect and of the same size as the object. |
| (b) A convex mirror |
(ii) Can form an image of objects spread over a large area. |
| (c) A convex lens |
(i) Used as a magnifying glass. |
| (d) A concave mirror |
(iii) Used by dentists to see an enlarged image of teeth. |
| (e) A concave lens |
(vi) The image is erect and smaller in size than the object. |
4. State the characteristics of the image formed by a plane mirror.
Answer:
Characteristics of the image formed by a plane mirror are as follows:
- Image distance and object distance are equal.
- The size of the object and image are equal.
- The image formed is erect and virtual.
- Images are laterally inverted.
5. Find out the letters of the English alphabet or any other language known to you in which the image formed in a plane mirror appears exactly like the letter itself. Discuss your findings.
Answer:
A, H, I, M, O, T, U, V, W, X, and Y alphabets form images in a plane mirror exactly like the letter itself because these alphabets are laterally symmetric.
6. What is a virtual image? Give one situation where a virtual image is formed.
Answer:
The image that cannot be obtained on a screen is called a virtual image. The image formed by a plane mirror is virtual.
7. State two differences between a convex and a concave lens.
Answer:
| Convex Lens |
Concave Lens |
| Thick in the middle and thin at the edge. |
Thin in the middle and thick at the edge. |
| The image formed is real or virtual. |
The image formed is virtual. |
8. Give one use each of a concave and a convex mirror.
Answer:
Concave mirrors are used in the headlights of cars and scooters.
Convex mirrors are used as side-view mirrors in vehicles.
9. Which type of mirror can form a real image?
Answer:
The concave mirror can form a real image.
10. Which type of lens always forms a virtual image?
Answer:
A concave lens forms a virtual image.
Choose the correct option in questions 11–13.
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:
Correct option is (ii) concave mirror.
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:
Correct option is (iii) 6 m
13. The rearview 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 rearview 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) 1 m/s
(ii) 2 m/s
(iii) 4 m/s
(iv) 8 m/s
Answer:
Correct option is (iii) 4 m/s.
