Question

What is the focal length of a plane mirror?

Answer 1

The focal length of a plane mirror.

1. The focal length of a plane mirror is infinity because parallel rays that meet after reflection via a plane mirror meet again at infinity.
2. A plane mirror has an unlimited focal length since it is a spherical mirror with an infinite radius of curvature.
3. We already know that focal length equals half the radius of curvature. As a result, the plane mirror's focal length is limitless.

Hence, the focal length of the plane mirror is infinite.