Thermal Radiation Behavior of Non-Black Bodies: I'm Confused!

In summary, the conversation discussed the confusion surrounding the thermal radiation behavior of non-black bodies. It was mentioned that non-black bodies do not necessarily emit the same color or spectral intensity as a black body, and that the amount of radiation emitted is equal to the amount absorbed. It was also noted that composition does not always play a role in color output, as seen in the blue flame of a blowing torch caused by the chemicals in the gas. However, the conversation ended with the understanding that Wikipedia provides a good explanation of this topic.
  • #1
carter7gindenv
14
1
Hello, I've searched a bit about about the thermal radiation behavior of non-black body and I'm confused.
I've read that the color is dependent only on the temperature so every thing display the same color as a black body.
But at the same time I've read that materials don't always follow the spectrum of a black body.

I've also read that composition plays no role in the color output however the blue flame of a blowing torch is due to the chemicals in the gas and not that it is as hot as a blue star.

I'm confused :frown:

Surely I'm not the only one asking that but I did not found a satisfying answer ( or did not use the wight words for searching )

Thanks for the help and nice week!
 
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  • #2
Non-black bodies do not necessarily emit the same color or spectral intensity as a black body.
However the amount of every wavelength in every direction of thermal radiation emitted by a body at temperature T, black or not, is equal to the corresponding amount that the body absorbs.
If the body emits a constant (over wavelength) fraction of the intensity of a perfect black it is usually called a gray body.
I believe wikipedia does a pretty good job on this subject.
 
  • #3
Thanks I think I got it.
 
  • Like
Likes hutchphd

1. What is thermal radiation and how does it behave in non-black bodies?

Thermal radiation is the transfer of heat through electromagnetic waves. In non-black bodies, the behavior of thermal radiation is affected by the body's color, surface properties, and temperature.

2. Why is it important to study the thermal radiation behavior of non-black bodies?

Understanding how non-black bodies emit and absorb thermal radiation is crucial in various fields such as engineering, materials science, and astrophysics. It can also help in developing more efficient heating and cooling systems.

3. How does the color of a non-black body affect its thermal radiation behavior?

The color of a non-black body determines its emissivity, which is the ability to emit thermal radiation. Darker colors have higher emissivity and thus can emit and absorb thermal radiation more efficiently.

4. Can the surface properties of a non-black body affect its thermal radiation behavior?

Yes, the surface properties such as texture and reflectivity can affect the emissivity and absorption of thermal radiation. Rougher surfaces have higher emissivity and absorb more thermal radiation compared to smoother surfaces.

5. How does the temperature of a non-black body impact its thermal radiation behavior?

The temperature of a non-black body affects the amount and wavelength of thermal radiation it emits. As the temperature increases, the body emits more thermal radiation, and the peak wavelength shifts to shorter wavelengths.

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