Question

The refractive index of a prism is $2$. The prism can have a maximum refracting angle of

• A. ${90}^{\circ }$
• B. ${60}^{\circ }$
• C. ${45}^{\circ }$
• D. ${30}^{\circ }$

Answer 1

Answer: (B)

${60}^{\circ }$

Critical angle ${\theta }_c={\sin }^{-1}\left(\frac{1}{\mu }\right)$

$={\sin }^{-1}\left(\frac{1}{2}\right)={30}^{\circ }$

If $A>2{\theta }_c$, the ray does not emerge from the prism. So, maximum angle can be ${60}^{\circ }$.