A concave mirror is placed in water. Will there be any change in its focal length? Give reason.

In the case of a spherical mirror, the'∠i' angle of incidence and '∠r' angle of reflection is responsible for the image formation.

The following diagram shows the nature of the focal length in a concave mirror when placed in water.

1. Law of reflection says that it is unaffected by the surrounding medium.
2. The focal length is independent of the medium where the spherical mirror is placed.

Therefore, there will be no change in the concave mirror focal length.