Prove that when a reflecting surface of light by an angle `theta`, the reflected light will be tited by an angle 20.

Explanation

For the reflecting surface AB. The incident ray IO and the reflected ray `OR_(1)` subtend angle I with the normal N as angle of incidence is equal to angle of reflection. When the surface AB us tilted to A.B. by an angle `theta`. Remember the position of incident ray IO remains unaltered. But, in the tilted system the angle of incidence is now `i+theta` and the angle of reflection is also `i + theta`. NOw, `OR_(2)` is the reflected ray. The angle between `OR_(2) and OR_(1)` is `angleR_(1)OR_(2) = angle N.OR_(2) - angleNOR_(1)`