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Blackbody radiation

  1. Dec 17, 2004 #1
    Sorry if my physics isnt so good. I only go to High school. Anywayz here is what i understand about blackbody radiation. A blackbody is an object that completely absorbs all the radiation of any wavelength. right. Then blackbody radiation means that a blackbody emitting radiation. Here is what i dont understand. If the object absorbs all the radiation then/how(2 questions) why does it emit it back. So the object is black at first due to absorbing all the light first and then it emits the light back. Did i get it right?

    Thnx for the help.
  2. jcsd
  3. Dec 17, 2004 #2


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    "Blackbody" means that the system is in thermodynamic equilibrium so that there is detailed balance balance between emitted and absorbed radiation. If there were no balance then the object would either be cooling or heating up.
  4. Dec 17, 2004 #3
    Thnx for replying Tide.

    I think i have an idea about what you said :uhh: so that would mean the object is absorbing and emitting radiation at the same time. Also is it true about the object being black first and the glowing due to emissions.

  5. Dec 17, 2004 #4


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    The use of "black" in the word "blackbody" is a little misleading. It was coined on the basis of the property of absorbing all the radiation that impinges on an object but that description leaves out the second equally important quality, namely that it also emits exactly as much radiation as it absorbs.

    The key property of a "blackbody" is that such an object is thermodynamic equilibrium.
  6. Dec 17, 2004 #5
    Thnx Tide for helping me.

    Its finally clear to me now i think :biggrin: . I am not up for this kinda stuff. Quantum theory is extremely complicated.

    Thnx again
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