Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site utastro.UUCP Path: utzoo!watmath!clyde!burl!ulysses!gamma!exodus!mhtsa!mh3bs!eagle!harpo!seismo!ut-sally!utastro!bill From: bill@utastro.UUCP Newsgroups: net.physics Subject: Re: Clouds Message-ID: <135@utastro.UUCP> Date: Mon, 20-Feb-84 18:00:20 EST Article-I.D.: utastro.135 Posted: Mon Feb 20 18:00:20 1984 Date-Received: Wed, 22-Feb-84 01:50:37 EST References: <2031@ecsvax.UUCP> Organization: UTexas Astronomy Dept., Austin, Texas Lines: 16 Clouds are white because of *diffraction*? No, they are white because they do not selectively absorb or reflect any particular color, but rather reflect all visible wavelengths with about equal efficiency. In the parliance of stellar atmospheres, they are grey bodies. The atmosphere as a whole, as has been pointed out, is an efficient scatterer of blue light (hence blue skies), and leaves in the red (hence red sunsets). When the clouds are pink, that is because they are reflecting the red light that falls on them after the blue has been removed. -- Bill Jefferys 8-% Astronomy Dept, University of Texas, Austin TX 78712 (USnail) {ihnp4,kpno,ctvax}!ut-sally!utastro!bill (uucp) utastro!bill@ut-ngp (ARPANET)