Thank you for reporting, we will resolve it shortly
Q.
If incident ray MP and reflected ray QN are parallel to each other, find the angle $\theta$ between the mirrors.
Ray Optics and Optical Instruments
Solution:
The deviation produced by first mirror $=180-2 i_1$
and the deviation produced by second mirror $=180-2 i _{2}$
The total deviation is $180^{\circ}$ as MP and $Q N$ are anti parallel
So, $180^{\circ}=360^{\circ}-2\left( i _{1}+ i _{2}\right)$
$\therefore i _{1}+ i _{2}=\theta=90^{\circ}$
