Question

A concave mirror of focal length \( f \) in air is dipped in a liquid of refractive index \( \mu \). Its focal length in the liquid will be:

• A. \( \frac{f}{\mu} \)
• B. \( \frac{f}{(\mu - 1)} \)
• C. \( \mu f \)
• D. \( f \)

Hint:

The focal length of a mirror is not affected by the refractive index of the medium, unlike lenses where the focal length changes with the refractive index of the medium.

Answer 1

The Correct Option is D

The focal length of a concave mirror is independent of the refractive index of the surrounding medium. It depends only on the curvature of the mirror. Therefore, when the mirror is dipped in a liquid with refractive index \( \mu \), the focal length remains the same as in air. Thus, the focal length in the liquid is: \[ \boxed{f}. \]