Question

A prism having refractive index $\sqrt{2}$ and refracting angle ${30}^o$, has one of the refracting surfaces polished. A beam of light incident on the other refracting surface will retrace its oath if the angle of incidence in:

• A. $0^o$
• B. ${30}^o$
• C. ${45}^o$
• D. ${60}^o$

Answer 1

The correct option is C ${45}^o$

$\begin{array}{c}Snel{l}^{\prime }slaw:\\ Refractiveindex,\mu =\frac{\sin i}{\sin r}\\ \sin i=\mu \sin r\\ =\sqrt{2}\times \sin {30}^0\\ =\sqrt{2}\times \frac{1}{2}\\ =\frac{1}{\sqrt{2}}\\ i={45}^0\\ Hence,\\ optionCiscorrectanswer.\end{array}$