The refractive indices of two media A and B are 2 and √ 2 respectively. What is the critical angle for their interface?

From Snell 's law:- \[\mu_{A} \sin i_{c}=\mu_{B} \operatorname{Sin} 90^{\circ} \] \(\displaystyle 2 \times \sin i_{c}=\sqrt{2} \times 1\) \(\displaystyle \sin i_{c}=\frac{1}{\sqrt{2}}\) \(\displaystyle i_{c}=45^{\circ}\) Alternatively: \[\begin{aligned} & \sin i_{c}=\frac{1}{{ }^{B} \mu_{A}} \\ & \sin i_{c}=\frac{1}{\sqrt{2}} \\ & i_{c}=45^{\circ} \end{aligned} \]