Question

Why Concave Mirrors Are Used In Tourches, Search Light And Headlight Of Vehicle

Answer 1

Light emitting devices, like bulbs produce light rays in all directions. But, in torches, search lights etc., it is required to focus the light in one direction. This is made possible by using a concave lens.

A ray of light passing through the focus is always reflected parallel to the principal axis. By placing a bulb at the focus, we can easily obtain a parallel beam of light.