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Path: utzoo!watmath!clyde!burl!ulysses!harpo!ihnp4!ihuxq!ken
From: ken@ihuxq.UUCP (ken perlow)
Newsgroups: net.physics
Subject: Re: Haloes on fogged-up glass...
Message-ID: <720@ihuxq.UUCP>
Date: Wed, 29-Feb-84 11:20:33 EST
Article-I.D.: ihuxq.720
Posted: Wed Feb 29 11:20:33 1984
Date-Received: Fri, 2-Mar-84 07:28:40 EST
References: <1201@ucf-cs.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 24

--
>>> Partly in consequence of seeing the haloes around the sun last week, I
>>> noticed that street lights seen through a fogged-up car windshield have
>>> a colored halo.  The strange thing was that there were areas of color,
>>> with no apparent order to where a particular color occured.

>>> My question, should anyone decide to accept it, is: 

>>> 	What causes the light to be broken up into colors?

A foggy (pun intended) recollection from a 1960's vintage optics
class:  Babinet's Principle.  I can't even remember what it is,
although it involves diffraction through multiple holes, and an
equivalence between such a situation and its logical inverse (multiple
points).  I do remember that haloes through foggy glasses was the
demonstration of Babinet's Principle.  (If I still had the text, I'd
restate the thing.)
-- 
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