A beam of light is traveling inside a solid glass cube having index of refraction 1.64. It strikes the surface of the cube from the inside.
(a) If the cube is in air, at what minimum angle with the normal inside the glass will this light not enter the air at this surface?
(b) What would be the minimum angle in part (a) if the cube were immersed in water? (The index of refraction of water is 1.333.)