A light ray is incident, at an incident angle $ heta_{1}$, on the system of two plane mirrors $M_{1

Question

A light ray is incident, at an incident angle $	heta_{1}$, on the system of two plane mirrors $M_{1}$ and $M_{2}$ having an inclination angle $75^{\circ}$ between them (as shown in figure).\ After reflecting from mirror $M_{1}$ it gets reflected back by the mirror $M_{2}$ with an angle of reflection $30^{\circ}$. The total deviation of the ray will be _______ degree.\

Professor PC Thomas Classes · Answer

(210) : Here,\ $75^{\circ}+60^{\circ}+90^{\circ}-	heta_{1}=180^{\circ} ; 	heta_{1}=45^{\circ}$\ So, total deviation is\ $\delta=360^{\circ}-2 	imes 75^{\circ}=210^{\circ}$\