Is white surface a good radiation emitter?


by tkm2002
Tags: emitter, radiation, surface, white
tkm2002
tkm2002 is offline
#1
Oct12-09, 08:31 AM
P: 8
In general, a good absorbers of radiation are also good emitters.
In commonsense, something that is should be a poor absorbers.
For example, we dress a white shirt in summer.

However, a experiment has done and shown that the radiation detected of black and white surface are very very close.For example,if the radiation detected of black surface is 14.9, the white surface is 14.7. What is reason about this phenomenon?

The experiment was used TD-8564A Radiation Cube that can be heated from room temperature to approximately 120 oC and the radiation detected is infrared.
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Bob S
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#2
Oct12-09, 04:02 PM
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Hi tkm-
"black" and "white" usually relate to the visual response light intensity. IR radiation from a warm surface, white or black, is a much longer wavelength,
Bob S.
reasonableman
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#3
Oct14-09, 04:52 PM
P: 80
I would say I'm surprised at this. I have seen pictures of a metal surface with rough patches and black tape taken with an infra-red camera and the rough patches appear a bit 'hotter' and the black tape appears a lot hotter.

What were the units of measurement and what frequency is this at? Also what are the 'surfaces' made of?

Born2bwire
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#4
Oct14-09, 11:58 PM
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Is white surface a good radiation emitter?


The problem is that our eyes only sense the visible light while a lot of the heat that we feel is in the infrared. So just because we see an object as white or black has no real bearing on their effectiveness of an absorber or reflector in spectrums that lie outside the visible range. It would not suprise me though that since the infrared range is right below the visible range that visible light absorption may be indicative of the infrared absorption. But this is not something that we can assume to be valid without further measurement, as you demonstrate in your OP.


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