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From: carl@aoa.UUCP (Carl Witthoft)
Newsgroups: net.sci
Subject: Re: Photon - Candlepower Quetion
Message-ID: <349@aoa.UUCP>
Date: Thu, 21-Nov-85 07:31:54 EST
Article-I.D.: aoa.349
Posted: Thu Nov 21 07:31:54 1985
Date-Received: Sat, 23-Nov-85 10:21:51 EST
References: <1095@mtuxo.UUCP> <567@ttrdc.UUCP>
Reply-To: carl@aoa.UUCP (Carl Witthoft)
Organization: Adaptive Optics Assoc., Cambridge, Mass. USA
Lines: 24

In article <567@ttrdc.UUCP> levy@ttrdc.UUCP (Daniel R. Levy) writes:
>In article <1095@mtuxo.UUCP>, 45223wc@mtuxo.UUCP (w.cambre) writes:
>>How many photons are there in one candlepower?
>Is this a hoax??  I thought candlePOWER was an expression of a RATE of energy
Come on , guys. the definition of candlepower, or candelas these days is 
easily available in CRC books or any reference text on optics. 
PHOTON is a quantum of energy (ignoring all the wave-particle duality stuff)
with a defined wavelength, momentum, etc.
CANDLEPOWER is all the power in all wavelengths emitted (in all directions)
by a standard source . This source was a candle long ago, but is now a 
black body at the solidification point (I think) of Platinum.

If W.Cambre was really asking how to convert candela to photons, the answer is
"it depends." That is, one needs to know what wavelength is involved, and
then play nasty games with integrals over blackbody curves. 
And dont forget lumens to nits/stilb conversions...( :==>)


Darwin's Dad ( Carl Witthoft @ Adaptive Optics Associates)
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