question_answer 63)

      Show that for a material with refractive index , light incident at any angle shall be guided along a length perpendicular to the incident face.

Answer:

                  In Pig. 6(EP).14, we have shown a ray of light incident at  on face AB . It is refracted at  and falls on face . This ray will suffer total internal reflection at K and proceed alone .                                                  or or                 Or           According to Snell's law,                                                                            will be smallest when                                             or         or,which was to be proved.