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 concave mirror of focal length f in air is dipped in a liquid. What is its focal length in the liquid?

Key concept: The focal length of a mirror depends only on the radius of curvature ($$f = R/2$$), which is a geometric property. Unlike a lens, a mirror's focal length does not depend on the refractive index of the surrounding medium.

Therefore, the focal length in the liquid remains f.

The correct answer is Option 2: f.