Question

Show, by ray diagram, how a totally reflecting glass prism can be used to deviate a ray through 180°.

Answer 1

Using the same 45°-90°-45° prism, if a ray enters normally on the hypotenuse face, it travels inside to meet one shorter face. At this face, total internal reflection occurs. The ray then meets the other shorter face and undergoes a second total internal reflection. After the second reflection, the ray emerges from the hypotenuse face in a direction exactly opposite to the incident ray, thus deviating it by 180°.