At what angle should a ray of light be incident on the face of a prism of refracting angle ${60}^{\circ }$ so that it just suffers total internal reflection at the other face. The refractive index of the prism is 1.524.

As shown in the figure, light is incident normally on one face of the prism. A liquid of refractive index $\mu$ is placed on the horizontal face $AC$. The refractive index of prism is $3/2$. If total internal reflection taken place on face $AC$, $\mu$ should be less than $\frac{I\sqrt{3}}{4}$, where $I$ is an integer. Find the value of $I$.