A ray of light passes through four transparent media with refractive indices`mu_1`,`mu_2`,`mu_3` and `mu_4` as shown in the figure. The surfaces of all media are parallel. If the emergent ray CD is parallel to the incident ray AB, we must have

Options

A. `nu_1 = mu_2`
B. `nu_2 = mu_3`
C. `nu_3 = mu_4`
D. `nu_4 = mu_1`

Answer

D