Question

The focal length of a concave mirror in the air is f. If it is immersed in water $(n=\frac{4}{3})$, then the focal length will be:

• A. $f$
• B. $\frac{4f}{3}$
• C. $\frac{3f}{4}$
• D. $4f$

Answer 1

The correct option is A

$f$

1. In the case of the concave mirror, there will be no change in the focal length of the mirror when immersed in water.
2. Therefore the focal length of the mirror is f.
3. It is because the focal length of the mirror does not depend on the external medium in which it is held.

Hence, option (A) is the correct answer.