Question

prove the focal length of spherical (concave) mirror is half of its radius of curvature.​

Answer 1

Answer:

Proving the focal length is half the radius of curvature:

Now the angle between the radius of curvature and principal axis will be equal to the angle at which ray is incident and due to reflections law incident angle would be equal to angle cbf. Hence, in both cases Radius is double the focal length.