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From: guy@slu70.UUCP
Newsgroups: sci.physics
Subject: Re: Why does light slow down?
Message-ID: <316@slu70.UUCP>
Date: Fri, 17-Oct-86 13:25:51 EDT
Article-I.D.: slu70.316
Posted: Fri Oct 17 13:25:51 1986
Date-Received: Tue, 21-Oct-86 20:37:29 EDT
References: <224@sri-arpa.ARPA> <3494@columbia.UUCP>
Distribution: net
Organization: Saint Louis University, St. Louis, MO
Lines: 10
Keywords: phase velocity, group velocity, Cerenkov radiation
Summary: crystals

In article <3494@columbia.UUCP>, zdenek@heathcliff.columbia.edu (Zdenek Radouch) writes:
> 2. GLASS
> 
> As usual, the more interesting case is when the waves travel in a material.
If you want an even more interesting case, look at crystalline  materials, which
are not only dispersive (i.e., group and phase velocity differ) but are also
anisotropic. This means that the polarization of the wave is a factor as well
as the velocity. This behavior is used extensively by geologists to identify
minerals using a polarizing microscope as each mineral passes polarized light
in a somewhat different fashion (yes, I know I've oversimplified).