= 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.
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