Question

A ray of light undergoes deviation of ${30}^{\circ }$ when incident on an equilateral prism of refractive index $\sqrt{2}$. The angle made by the ray inside the prism with the base of the prism is

• A. ${15}^{\circ }$
• B. $0^{\circ }$
• C. ${45}^{\circ }$
• D. ${30}^{\circ }$

Answer 1

The correct option is B $0^{\circ }$

$\mu =\sqrt{2},A={60}^{\circ },\delta ={30}^{\circ }$
For the minimum deviation
$\mu =\frac{sin\left(\frac{A+{\delta }_m}{2}\right)}{sin\left(\frac{A}{2}\right)}$
Substituting the values of A and $\mu$ we see that ${\delta }_m={30}^{\circ }$
i.e., the given deviation ${\delta }_m.$ At minimum deviation the ray inside the prism is parallel to the base in case of an equilateral prism.