A monochromatic light is incident on the plane interface AB between two media of refractive indices `mu_(1)` and `(mu_(2)gtmu_(1))` at an angle of incidence `theta` as shown in Fig.
The angle `theta` is infinitesimally greater than the critical angle for the two media so that total internal reflection takes place. Now, if a transparent slab DEFG of uniform thickness and of refractive index `mu_(3)` is introduced on the interface (as shown in the figure), show that for any value of `mu_(3)` all light will ultimately be reflected back into medium II.