Dispersion refers to the observed dispersion of microwave radiation when it encounters an obstruction. Perhaps the most common form of dispersion is that of light, when it encounters an object and is reflected back in wavelengths that the human eye perceives as colors. Dispersion theory also has many uses in nonrelativistic quantum mechanics, in wave motion, and in sound mechanics.

The ratio of light's velocity in a substance to its velocity in a vacuum is called the index of refraction. It is represented by the equation n = c/v, where n is the index of refraction, c is the absolute speed of light in a vacuum, and v is the light's observed velocity while passing through a substance. In almost every case the index of refraction is equal to or greater than one. The refraction of light depends on passage either through a medium with varying index of...