The problem asks for the radius of curvature of a plane mirror. The possible answers are: (a) Zero, (b) Unity, (c) Finite, (d) Infinite.

1. Problem Description

The problem asks for the radius of curvature of a plane mirror. The possible answers are: (a) Zero, (b) Unity, (c) Finite, (d) Infinite.

2. Solution Steps

A plane mirror is flat. If we consider a curved mirror, its curvature is related to the radius of the sphere from which the mirror is a part. A plane mirror can be thought of as a part of a sphere with a very large radius. As the radius of the sphere increases, the curvature decreases, and as the radius approaches infinity, the curvature approaches zero.

Therefore, a plane mirror has an infinite radius of curvature.

3. Final Answer

(d) Infinite