Q. The refractive index of the material of a prism is $\sqrt{2}$ and the angle of prism is $30{^\circ}.\ $One of its refracting faces is polished. The incident beam of lift will retrace back for angle of incidence
A) $0{^\circ}$
B) $45{^\circ}$
C) $60{^\circ}$
D) $90{^\circ}$
Explanation
(b) $A = r_{1} + r_{2}$
$\therefore 30{^\circ} = r_{1} + 0{^\circ}$
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or$\ \ r_{1} = 30{^\circ}$
Now,$\ \frac{\sin i}{\sin{30{^\circ}}} = \sqrt{2}$
or${\ \ sin}{i = \sqrt{2} \times \frac{1}{2}}$
Or $\ \sin{i = \frac{1}{\sqrt{2}}}$
Or $i = 45{^\circ}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.