Question

A ray of light travelling in a transparent medium falls on a surface separating the medium from air, at an angle of incidence of ${45}^{\circ }$. The ray undergoes total internal reflection. If $n$ is the refractive index of the medium with respect to air, select the possible values of $n$ from the following.

• A. $1.3$
• B. $1.4$
• C. $1.5$
• D. $1.2$

Answer 1

The correct option is C $1.5$

Given,

Angle of incidence=${45}^0$

We know,

For Total Internal Reflection,

$i>{\sin }^{-1}\left(\frac{1}{\mu }\right)$

$sin\left(i\right)>\frac{1}{\mu }$

$\mu >\frac{1}{\sin i}$

$\mu >\sqrt{2}=1.44$

$\mu >1.44$

Only option which satisfies is $\mu =1.5$

Option $\text{C}$ is correct answer.