On Wed, 3 Jul 2002, Brendan Moran wrote:

>> It is.  You want the surface to be able to maximally radiate at all
>> wavelengths, therefore black.  Ideally the surface becomes a "black body"
>> radiator.
>
>I am probably remembering something wrong, but my thought would be that if
>you don't want the sink to pickup stray radiation from the surrounding
>environment and have to radiate it too, then black is the wrong colour to
>use.  I thought that blackbody radiation was simply for a situation where
>reflected energy was ignored.  With a sink, don't you want it to reflect
>energy and thereby have less to deal with?

The sink will pick up stray radiation from the surrounding but it will
radiate itself SIGNIFICANTLY more than that because it is hotter. The gain
obtained like this far outweighs losses due to captured radiation. The
black effectively improves the radiation coupling of the object to the
medium, in both directions.

Peter

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