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From: bobr@zeus.UUCP (Robert Reed)
Newsgroups: net.cooks,net.flame
Subject: Re: Truth in Advertising? (black bodies)
Message-ID: <411@zeus.UUCP>
Date: Tue, 13-Nov-84 16:08:01 EST
Article-I.D.: zeus.411
Posted: Tue Nov 13 16:08:01 1984
Date-Received: Fri, 16-Nov-84 01:22:01 EST
References: <2559@dartvax.UUCP>, <642@watdcsu.UUCP> <216@pyuxt.UUCP>
Organization: Tektronix, Beaverton OR
Lines: 21

regarding black bodies

    "There are some substances, such as lampblack, whose absorptivity is very
    nearly unity.  For theoretical purposes it is useful to conceive of an
    ideal substance capable of absorbing all the thermal radiation falling
    on it.  Such a substance is called a blackbody.

    "...the irradiance within a cavity whose walls are at the temperature
    *theta* is equal to the radiant emittance of a blackbody at the same
    temperature.  For this reason, the radiation within a cavity is called
    blackbody radiation.  ...  Since [irradiance] is independent of the
    materials of which the interior walls are composed, it follows that the
    radiant emittance of a blackbody is a function of the temperature only."

    [from "Heat and Thermodynamics" by Mark W. Zemansky]

Thus blackbody refers to the absorptive qualities of a material.  I hope
this ends the speculation I've seen here recently, and we can get on to
topics more germaine to this newsgroup.
-- 
Robert Reed, Logic Design Systems Division, tektronix!teklds!bobr