A beam of light converges to a point on a screen S A mirror

Last updated: 6/9/2023

A beam of light converges to a point on a screen S A mirror is placed in front of the screen at a distance of 10 cm from the screen It is found that the beam now converges at a point 20cm in front of the mirror Find the focal length of the mirror A 10 cm B 20 cm C 30 cm D 40 cm