Question

The critical angle for a medium with respect to air is ${45}^o$. The refractive index of that medium with respect to air is

• A. $\frac{\sqrt{3}}{2}$
• B. $\frac{2}{\sqrt{3}}$
• C. $\sqrt{2}$
• D. $\frac{1}{\sqrt{2}}$

Answer 1

The correct option is C $\sqrt{2}$

Critical angle ${\theta }_c={45}^o$

For total internal reflection

$n_{medium}sin{\theta }_c=n_{air}$ , the refractive index of air is 1

$n_{medium}sin{\theta }_c=1$

$n_{medium}=\frac{1}{sin45}=\sqrt{2}$