Hendrik Antoon Lorentz.

Title: Lorentz, Hendrik Antoon (1853-1928) Date: 01-01-1998 Publication: The Hutchinson Dictionary of Scientific Biography http:www.encyclopedia.com Author: None Lorentz, Hendrik Antoon (1853-1928) was a Dutch physicist who helped to develop the theory of electromagnetism, which was recognized by the award (jointly with his pupil Pieter Zeeman) of the 1902 Nobel Prize in Physics. Lorentz was born in Arnhem, Holland, on 18 July 1853. He was educated at local schools and at the University of Leyden, …

…nequal rate of propagation of the beams of light in different substances. How does it come about, however, that the speed of light in solid, liquid, and gaseous substances differs from its speed in the ether of empty space, so that it has its own value for each of these ponderable substances; and how can it be explained that these values, and hence also the refractive index, vary from one colour to another.