JEE PYQ: Ray Optics Question 45
Question 45 - 2019 (09 Jan Shift 2)
Two plane mirrors are inclined to each other such that a ray of light incident on the first mirror ($M_1$) and parallel to the second mirror ($M_2$) is finally reflected from the second mirror ($M_2$) parallel to the first mirror ($M_1$). The angle between the two mirrors will be:
(1) 45$°$
(2) 60$°$
(3) 75$°$
(4) 90$°$
Show Answer
Answer: (2)
Solution
Let angle between the two mirrors be $\theta$. Ray PQ $\parallel$ mirror $M_1$ and RS $\parallel$ mirror $M_2$ $\therefore M_1$RS $= \angle$ORQ $= \angle M_1$OM$_2 = \theta$ Similarly, $\angle M_2$QP $= \angle$OQR $= \angle M_2$O$M_1 = \theta$ $\therefore$ In $\triangle$ORQ, $3\theta = 180° \Rightarrow \theta = \frac{180°}{3} = 60°$
BETA
