A ray of white light in air passes by a glass plate. Refraction takes place. The direction in which the light is travelling changes. For what colour of light is the alteration in direction red, greater or blue?

Ans:

The index of refraction of a transparent medium is usually pretty much the same for every visible wavelength but not quite. The reality that the index of refraction does depend on the wavelength of the light is what makes it so that a prism breaks up white light into a rainbow of colours. When white light a mix of all the observable wavelengths enters a glass or quartz prism from air for instance the violet light gets refracted a little bit more toward the normal than the other colours and on leaving the prism it gets refracted a little bit more away from the normal than the other colours. The effect takes place for all the wavelengths with the shorter wavelengths being refracted more and the longer wavelengths are refracted les. The effect is the rainbow of colours that we see when white light passes through a prism.

Here we demonstrate the effect for the case of a prism but we leave out all the colours except for green, red and violet.