NCERT Solutions For Class 7 Science Chapter 15 Exercise
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.
Solution:
(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. (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 forms a real image. (T/F)
Solution:
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. |
Solution:
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.
Solution:
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.
Solution:
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.
Solution:
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.
Solution:
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. |