Question

If the radius of curvature of a spherical mirror is 20 cm, then its focal length is _______ cm.

• A. 20
• B. 10
• C. 40
• D. None of these

Answer 1

Answer: (B)

Radius of curvature = 2 x focal length.
So, focal length = $\frac{1}{2}\times$ radius of curvature = $\frac{1}{2}\times 20$ cm = 10 cm