A point object is placed on the principal axis of a concave mirror quite far away from the pole
Channel: Doubtnut
Date: 2020-01-26

A point object is placed on the principal axis of a concave mirror quite far away from the pole and moved at a constant speed `0.5 cm//sec` towards the pole. Its image also moves. It is found that the object and the image cross each other at a point which is at a distance 50 cm from the pole. Focal length of the mirror is -