Question

A ray of light is incident upon a parallel sided transparent slab of thickness 9 cm at an angle of incidence 60${}^{\circ }$. If the angle of refraction is 30${}^{\circ }$, the lateral displacement of the light ray is :

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

Answer 1

Answer: (B)

3 $\sqrt{3}$ cm

$Given:t=9cm,i={60}^{\circ },r={30}^{\circ }Distancetravelledbylightinsideglassslabd=\frac{t}{\cos \left(r\right)}=\frac{9cm}{\cos \left({30}^{\circ }\right)}=6\sqrt{3}cmLateraldisplacement=\left|d\sin \delta \right|(where\delta =r-i)=\left|6\sqrt{3}\sin ({30}^{\circ }-{60}^{\circ })\right|=3\sqrt{3}cm$