Refraction + Reflection. A flat mirror is placed at a right angle with a long dielectric slab with index of refraction n as shown. A beam of light in air is incident on the dielectric slab at an angle a = 60 and is refracted at an angle = 30'. (a) What is the value of n? (b) The beam of light undergoes a second refraction as it goes out of the slab. It then hits the mirror and gets reflected in air at an angle Y. What is the value of y? (c) At what values of will the beam be confined within the dielectric slab?