 Solution

The result need not be the same. Optical dispersion changes the refractive index with wavelength. Under normal dispersion, the blue-light index is larger, changing the refracted rays and generally reducing the visible fraction in the one-interface model. The blue indices of both water and glass are not specified; they may also differ from each other, introducing refraction at their interface. Thus no unique numerical blue-light fraction follows from the red-light value alone.