Question

The radius of curvature of a spherical mirror is 40 cm.

Calculate its focal length.​

Answer 1

it is a formula

R = 2f

40 = 2f

f = 20 cm.

there you go :)

Answer 2

Answer:

$we \: know \: that , \\ \: radius \: of \: curvature = 2 \: times \: of \: focal \: lenght \: \\ = > 40 = 2f \\ = > f = \frac{40}{2} \\ = > f = 20 \: cm \:$

focal length = 20 cm