Question

1. Define the principal focus of a concave mirror.
2. The radius of curvature of a spherical mirror is 20 cm. What is it​

Answer 1

Explanation:

all the lines parallel to principal axis of a concave mirror appear to meet at a point.This is called principal focus of concave mirror .It is denoted by F.

R=20 cm

so its focal length is

R=2f

f=R/2

f=20/2=10 cm