Question

A ray of light is incident on a plane mirror placed horizontally. When the mirror is rotated through an angle `30^(@)` the reflected ray is found to be directed along the vertical. Determine the angle of incidence at the initial position of the mirror.

Answer 1

(i) When a plane mirror is rotated through an angle `theta`, the reflected ray is rotated through 2`theta`.
The initial angle of incidence `i_(1) = i_(2) + r_(2)`
When `i_(2) and r_(2)` are the angle of incidence and angle of reflection after rotating the mirror.
(ii) ` 60^(@)`