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