Black Body

On 09/12/2016 12:04, David Levy wrote:
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Do you expect that the internal radiation in that bar will also have a
black body signature?-
'Poutnik[_5_ Wrote:

Sure. There is no cavity with thermal radiation absent. If cavity
opening is negligible, the radiation can be considered as BB. Note that
if multiple cavities are connected, so there is option of radiative
equilibrium between them, the requirement of the negligible opening is
not valid any.
This bar goes to infinity.
So the question is as follow:
Do we need to close it at the end of the infinity?
If I understand it correctly:
1. Theoretically, There is no end for infinity. Hence, if the radiation
is moving in the direction of the infinity – it will never bump a
wall. Therefore, there is no need to close it.
2. The Energy of the radiation is decreasing as it moves. If it moves to
the infinity, then at some point it should be virtually Zero. If the
energy of that radiation is Zero, then it will never come back even if
we set a wall. Hence, again – there is no need to close it at the
infinity.
So, my conclusion is – if we look at a bar which goes to the
infinity – it must have five walls which fulfill the requirements
for insulated enclosure while the one which goes to the infinity can
stay open without damaging the Black body signature.
Do you agree with that?

Sigh. We can add "infinity" to the long list of concepts that you
fundamentally have made no attempt to understand.


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Regards,
Martin Brown