Question

A ray of light passes through an equilateral glass prism in such a manner that the angle of incidence is equal to the angle of emergence and each of these angles is equal to $\frac{3}{4}$ of the angle of the prism. The angle of deviation is

• A. ${45}^{\circ }$
• B. ${39}^{\circ }$
• C. ${20}^{\circ }$
• D. ${30}^{\circ }$

Answer 1

The correct option is D ${30}^{\circ }$

Given that $A={60}^{\circ }$ and $i=\frac{3}{4}A=\frac{3}{4}\times 60={45}^{\circ }$
By using $i+e=A+\delta \Rightarrow 45+45=60+\delta \Rightarrow \delta ={30}^{\circ }$