dispersion

In physics, a particular property of refraction in which the angle and velocity of waves passing through a dispersive medium depend upon their frequency. When visible white light passes through a prism it is split into a spectrum (see electromagnetic waves). This occurs because each component frequency of light, which corresponds to a colour, is refracted by a slightly different angle, and so the light is split into its component frequencies (colours). A rainbow is formed when sunlight is dispersed by raindrops.

A white light beam splits up into the colours of which it consists (red, orange, yellow, green, blue, indigo, and violet). Red light has the lowest frequency (longest wavelength) and is the least refracted; violet light has the highest frequency (shortest wavelength) and is the most refracted. The relationship between wavelength and frequency is given by the formula: speed of light = frequency × wavelength (or wavelength = speed of light/frequency).