Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!burl!mgnetp!ihnp4!zehntel!hplabs!sri-unix!bradford@Amsaa.ARPA
From: bradford@Amsaa.ARPA
Newsgroups: net.physics
Subject: What polishing does to the surface of rocks.
Message-ID: <599@sri-arpa.UUCP>
Date: Wed, 1-Aug-84 08:33:15 EDT
Article-I.D.: sri-arpa.599
Posted: Wed Aug  1 08:33:15 1984
Date-Received: Sat, 4-Aug-84 03:45:27 EDT
Lines: 17

From:      Pete Bradford (CSD UK) 

	In answer to a couple of queries that I have received on
my comment that if you grind up a substance finely enough it will
appear black, here is a simple explanation.

	Once the particle size becomes smaller than a value which
is approximately the wavelength of light, radiation of that wave-
length can no longer be affected by the said particles. no reflect-
ion therefore takes place (no absorption either, presumably) and
the 'powder' appears black.

	This is presumably the answer to Gilman's question about
Xerox toner.


				PJB