Question

Under minimum deviation condition in a prism, if a ray is incident at an angle 30${}^o$, the angle between the emergent ray and the second refracting surface of the prism is :

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

Answer 1

The correct option is D 60${}^o$

Observing the figure, the minimum deviation phenomenon occurs when $i_1=i_2$

Thus, the angle of emergence = $i_2={30}^o$

But, this is the angle between the normal to the prism and the emergent ray.

Thus, angle between the prism surface and the emergent ray is ${90}^o-i_2={90}^o-{30}^o={60}^o$