Question

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

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

Answer 1

The correct option is B $\sqrt{3}$

$r_2=0^{\circ }$
$\therefore r_1=a={30}^{\circ }$
And $i_1={60}^{\circ }$
$\therefore \mu =\frac{sin{60}^{\circ }}{sin{30}^{\circ }}=\sqrt{3}$