Consider a glass prism whose cross-section is an equilateral triangle. A ray of purple light is incident on the prism from the left, travelling parallel to its base. What is the angular displacement of the red and blue rays that emerge from the right-hand side of the prism? Does the red ray emerge above the blue ray, or vice versa? The refractive indices of red and blue light in glass are 1.513 and 1.528 respectively.