Question

The radius of a curvature of a spherical mirror is 40cm. What is it's focal length

Answer 1

Answer:

the focal length will be 20 cm.

Explanation:

because the focal length is half of the radius of curvature.

Answer 2

Focal length of a plane mirror is infinity. (A plane mirror can be considered as a spherical mirror of infinite radius of curvature. Focal length is half of radius of curvature and hence it is infinity.