Q.
A ray of light enters a glass sphere, and after three total internal reflections it travels into original direction as shown in the figure. If $\mu$ is the refractive index of sphere, then the relation between $\mu$ and $\beta$ is expressed $\sin ^{2} x \beta+$ $\mu^{2} \sin ^{2} \beta=1$. Find the value of $x$.
Ray Optics and Optical Instruments
Solution: