Optics Problem! PLEASE HELP ASAP?

In an equilateral prism with a horizontal base, the dispersion of white light is most easily seen when the refracted light in the middle of the visible spectrum (yellow) is parallel to the base of the prism. Determine the angle of incidence of yellow light in air that creates this situation in a prism made of crown... show more In an equilateral prism with a horizontal base, the dispersion of white light is most easily seen when the refracted light in the middle of the visible spectrum (yellow) is parallel to the base of the prism. Determine the angle of incidence of yellow light in air that creates this situation in a prism made of crown glass.

n crown glass = 1.52
n yellow light in air = 1.517