$A$ transparent cube of side $d$,made of a material of refractive index $\mu_2$,is immersed in a liquid of refractive index $\mu_1$ (where $\mu_1 < \mu_2$). $A$ ray is incident on the face $AB$ at an angle $\theta$ (as shown in the figure). Total internal reflection takes place at point $E$ on the face $BC$. The angle $\theta$ must satisfy:

• A
  $\theta > \sin^{-1} \left( \frac{\mu_1}{\mu_2} \right)$
• B
  $\theta > \sin^{-1} \sqrt{\frac{\mu_2^2}{\mu_1^2} - 1}$
• C
  $\theta < \sin^{-1} \left( \frac{\mu_1}{\mu_2} \right)$
• D
  $\theta < \sin^{-1} \sqrt{\frac{\mu_2^2}{\mu_1^2} - 1}$