Question

One of the refracting surfaces of a prism of angle ${30}^{\circ }$ is silvered. A ray incident at angle of ${60}^{\circ }$ retraces its path. The refractive index of the material of prism is

• A. $\sqrt{2}$
• B. $\sqrt{3}$
• C. $3/2$
• D. $2$

Answer 1

Answer: (B)

$\sqrt{3}$

$r_2={\theta }^{\circ }$
$r_1=A={30}^{\circ }$
and $i_1={60}^{\circ }$
$\mu =\frac{\sin i_1}{\sin r_1}=\frac{\sin {60}^{\circ }}{\sin {30}^{\circ }}=\sqrt{3}$.