A ray of light is incident at an angle of `60^(@)` on a horizontal plane mirror. Through what angle should the mirror be tilted to make the reflected ray horizontal ?

Answer

`15^(@)`

Explanation

To make the reflected ray horizontal, it must be turned further through `90^(@) - 60^(@) = 30^(@)`. Therefore, the mirror must be turned through `30//2 = 15^(@)`