Question

When a ray of light is incident normally on one refracting surface of an equilateral prism (Refractive index of the material of the prism$=$1.5)

• A. emerging ray is deviated by ${30}^{\circ }$
• B. emerging ray is deviated by ${45}^{\circ }$
• C. emerging ray just grazes the second refracting surface
• D. The ray undergoes total internal reflection at the second refracting surface

Answer 1

The correct option is D The ray undergoes total internal reflection at the second refracting surface

the ray undergoes total internal reflection at the second refracting surface.

$\mu =\frac{1}{\sin C}=\frac{1}{\sin 60}=\frac{2}{\sqrt{3}}$

$\sin C=\frac{1}{\mu }\Rightarrow C={\sin }^{-1}\frac{2}{3}\cong {42}^{\circ }$

$\theta <{45}^{\circ }$