Radius of curvature of a spherical mirror = 2 × Focal length (f)R= 2f

f= R/2 = 20 / 2 = 10

Hence, the focal length of the given spherical mirror is 10 cm.

Radius of curvature = 2 × Focal length (f)

R= 2ff= R/2 = 32/2 = 16

Hence, the focal length of the given convex mirror is 16 cm.