a) A beam of light traveling in a block of glass (n=1.60) is incident on the top surface at an angle of 55° with respect to the normal. When a layer of oil is placed on the top surface, the light is totally reflected in the glass. What is the maximum possible index of refraction of the oil?
b) You look at the center of one face of a solid cube of glass on a line of sight that makes a 55° angle with the normal to the cube face. What minimum refractive index of the glass will let you see through the cube's opposite face?