Dispersion.

Dispersion. The refractive index of a transparent medium is different for different kinds of light. Thus, when white light passes through a given prism, the rays of different refrangibility of which it is composed are bent by different amounts from their original common direction. They are said to be dispersed. The dispersion for the given prism depends upon the difference of the refractive indices of the extreme rays of the visible spectrum. It varies with the substance and the angle of the prism. The relative breadth of any two parts of the spectrum varies with the substance of the prism. This constitutes the so-called irrationality of dispersion. In general, rays of short wavelength are more refracted than rays of long wavelength, but in some refracting media this law breaks down in part. This is known as anomalous dispersion. The term false dispersion is applied to the scattering of light by reflection from motes suspended in a transparent medium. See LIGHT.