Is white surface a good radiation emitter?

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Discussion Overview

The discussion centers on the effectiveness of white surfaces as radiation emitters compared to black surfaces, particularly in the context of infrared radiation. Participants explore the relationship between color, absorption, and emission of radiation, referencing experimental observations and theoretical considerations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that good absorbers of radiation are typically also good emitters, suggesting a common understanding that white surfaces should be poor absorbers and emitters.
  • Another participant points out that the terms "black" and "white" relate to visual light intensity, while infrared radiation involves longer wavelengths, which may not correlate directly with visible properties.
  • A participant expresses surprise at the experimental findings, mentioning observations of different surface temperatures in infrared imaging and inquiring about measurement units and surface materials.
  • It is suggested that visible light absorption may not accurately predict infrared absorption, emphasizing the need for further measurements to validate assumptions about color and radiation properties.

Areas of Agreement / Disagreement

Participants do not reach a consensus; there are competing views regarding the relationship between surface color and radiation emission, and the discussion remains unresolved.

Contextual Notes

Limitations include the dependence on specific experimental conditions, the nature of the surfaces being tested, and the need for clarity on measurement units and frequencies involved in the observations.

tkm2002
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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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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.
 
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 infrared 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?
 
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 surprise 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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