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 10cm from the screen. It is found that the beam now converges at apoint 20cm in front of the mirror. Find the focal length of the mirror.
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 10cm from the screen. It is found that the beam now converges at apoint 20cm in front of the mirror. Find the focal length of the mirror.










