As shown in the figure, white light enters a 45-90-45 crown glass prism at the vertical face.

As shown in the figure, white light enters a 45-90-45 crown glass prism at the vertical face. Part of this light refracts at the slanted face into the surrounding material and the rest experiences total internal reflection and exits the prism at the horizontal base. The colors of light that emerge from the slanted face may be chosen by varying the index of refraction of the material surrounding the prism. Determine the required index of refraction of the surrounding material for each of the following cases.