Encyclopedia … combined with a great Buyer's Guide!

Sponsorship opportunity: support this popular resource, which serves the whole photonics community, and get recognition!

Principal Dispersion

Definition: a crude measure for chromatic dispersion of a transparent optical material

German: Hauptdispersion

Category: general optics

How to cite the article; suggest additional literature


The principal dispersion is a rather crude measure for chromatic dispersion of an optical material in the visible spectral region, which was developed in the early years of optics. It is simply the difference of refractive indices between two specific standard spectral lines of hydrogen:

The principal dispersion nF − nC appears in the definition of the Abbe number.

In photographic optics, the principal dispersion is often based on two somewhat different spectral lines of cadmium:

See also: chromatic dispersion, refractive index, Abbe number
and other articles in the category general optics


If you like this article, share it with your friends and colleagues, e.g. via social media: