Page 97 - Physics - XII

Assertion-Reason Type Questions

These consist of two statements—Assertion (A) and Reason (R). Answer these questions by selecting
the appropriate option given below:
a. Both A and R are true and R is the correct explanation of A.

b. Both A and R are true and R is not the correct explanation of A.
c. A is true but R is false.
d. A is false but R is true.

1. Assertion (A) : A double convex lens (µ = 1.5) has focal length 10 cm. When the lens is immersed
in water (µ = 4/3) its focal length becomes 40 cm.

Reason (R) : 1 g m 1 1
f m R 1 R 2

2. Assertion (A) : Refractive index has no unit.

Reason (R ) : The refractive index is a ratio of two similar quantities.
3. Assertion (A) : It is not possible to see a virtual image by eye.

Reason (R) : The rays that appear to be coming from a virtual image are not actually coming
from the image.

4. Assertion (A) : The focal length of a convex mirror is 20 cm. If a real object is placed at a
distance of 20 cm from the mirror, its virtual, erect, and diminished image will be
formed.

Reason (R) : If a virtual object is placed at 20 cm distance behind the convex mirror, its image
is formed at infi nity.
5. Assertion (A) : If the angles of the base of the prism are equal, then in the position of minimum
deviation, the refracted ray will pass parallel to the base of prism.

Reason (R) : In the case of minimum deviation, the angle of incidence is equal to the angle of
emergence.

Answer key

1. (a), 2. (a), 3. (d), 4. (b), 5. (a)

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