Light enters at right angle through one of the catheti of a right-angle isosceles prism which is made of glass with an index of refraction of 1.620. Because the angle of the ray with the normal when entering into the glass is zero, the ray passes straight through and strikes the interior of the hypotenuse of the prism. What is the largest value for the index of refraction of the surrounding medium which would still cause total internal reflection inside the prism?

Light enters at right angle through one of the catheti of a right-angle isosceles prism which is made of glass with an index of refraction of 1.620. Because the angle of the ray with the normal when entering into the glass is zero, the ray passes straight through and strikes the interior of the hypotenuse of the prism. What is the largest value for the index of refraction of the surrounding medium which would still cause total internal reflection inside the prism?