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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)
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