NCERT Solutions for Class 7 Science Chapter 15 Light
Exercises
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) An image that cannot be obtained on a screen is called 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.
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. (T/F)
(b) A concave lens always form a virtual image. (T/F)
(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T/F)
(d) A real image cannot be obtained on a screen. (T/F)
(e) A concave mirror always form a real image. (T/F)
Answer:- a) False
- b) True
- c) True
- d) False
- e) False
Question:- 3. 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 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 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 enlarged image of teeth. |
(e) A concave lens
| (vi) The image is erect and smaller in size than the object. |
Question:- 4. State the characteristics of the image formed by a plane mirror.
Answer:- Following are the Characteristics of the image formed by a plane mirror:-
- The distance of Image is equal to the distance of object.
- The size of object is equal to the size of image.
- The image formed is always erect and virtual
- Images are laterally inverted.( i.e our right look left in plane mirror)
Question:- 5. Find out the letters of 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, Y.
Question:- 6. What is a virtual image? Give one situation where a virtual image is formed.
Answer:- The image that we cannot obtain on a screen is called a virtual image. The image formed by a plane mirror is virtual image.
Question:- 7. State two differences between a convex and a concave lens.
Answer:-
Convex Lens | Concave Lens |
They are thick in the middle and thin at the edge | They are Thin in the middle and thick at the edge |
Image formed by them is real or virtual | Image formed by them is virtual |
Question:- 8. Give one use each of a concave and a convex mirror.
Answer:- Concave mirrors are used by dentists to see an enlarged image of the teeth.
Convex mirrors are used as side view mirror in vehicles.
Question:- 9. Which type of mirror can form a real image?
Answer:- Concave mirrors
Question:- 10. Which type of lens forms always a virtual image?
Answer:- Concave lens.
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:- (ii) concave 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:- (iii) 6 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) 1 m/s (ii) 2 m/s
(iii) 4 m/s (iv) 8 m/s
Answer:- (iii) 4 m/s