Q. A ray $PQ$ incident on the refracting face $BA$is refracted in the prism $BAC$as shown in the figure and emerges from the other refracting face $AC$as $RS,$such that $AQ = \ AR.$If the angle of prism $A = \ 60{^\circ}$ and the refractive index of the material of prism is $\sqrt{3},$ then the angle of deviation of the ray is
A) $60{^\circ}$
B) $45{^\circ}$
C) $30{^\circ}$
D) None of these
Explanation
(a) For a given prism, the angle of deviation depends upon the angel of incidence of the light rays falling on the prism
Taking triangle $F\ PQR$, we have
$S = \ \angle FQR + \angle FRQ$
Since, $\mathrm{\Delta}AQR\ $is an equilateral triangle, therefore,
$\angle FQR = \frac{60{^\circ}}{2} = 30{^\circ} = \angle FRQ$
$\therefore\ \delta = 30{^\circ} + 30{^\circ} = 60{^\circ}$
Hence, angle of deviation of the ray is $60{^\circ}.$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.