Q. An isosceles prism of angle $120{^\circ}$ has a refractive index of 1.44. Two parallel monochromatic rays enter the prism parallel to each other in air as shown. The rays emerging from the opposite faces
A) Are parallel to each other
B) Are diverging
C) Make an angle $2\sin^{- 1}{(0.72)}$ with each other
D) Make an angle $2\{\sin^{- 1}{(0.72) - 30{^\circ}}\}$ with each other
Explanation
(d) At point $A.\frac{\sin{30{^\circ}}}{\sin r} = \frac{1}{1.44}$
$\Rightarrow r = \sin^{- 1}(0.72)$ also $\angle BAD = 180{^\circ} - \angle r$
In rectangular $ABCD,\ \angle A + \angle B + \angle C + \angle D = 360{^\circ}$
$\Rightarrow (180{^\circ} - r) + 60{^\circ} + (180{^\circ} - r) + \theta = 360{^\circ}$
$\Rightarrow \theta = 2\lbrack\sin^{- 1}(0.72) - 30{^\circ}\rbrack$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.