Question

The refractive index of the material of a prism is $\sqrt{2}$ and the angle of the prism is 30°. One of the two refracting surfaces of the prism is made a mirror facing inwards by silver coating. A beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface), if its angle of incidence on the prism is

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

Answer 1

The correct option is B ${45}^0$


r2 = 0°

r1 = A = 30°

sin i = μ sin r

sin i = $\sqrt{2}$ sin30°

$\Rightarrow$ $\sqrt{2}$ ×1/2 = 1/$\sqrt{2}$

sin i=1/$\sqrt{2}$

∠i = 45°