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I Energy lost through photon emission

  1. Nov 9, 2018 #1
    Hey guys, new here. Here is my first question for the forums: Let's say that I have a controlled environment for an experiment whereby I want to heat, say, one cubic centimeter of steel until it is white hot. Assuming that I have perfect containment set up for it such that no energy can be transferred out of the material after it has been heat-charged, thus not allowing it cool, how long would it emit photons before going dark? Thanks.
     
  2. jcsd
  3. Nov 9, 2018 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF. :smile:
    So photon emission does not carry any energy away?

    And are you familiar with the topic of block body emission yet?
     
  4. Nov 9, 2018 #3
    Would Stefan–Boltzmann law suffice? As for how long, It will always emit photons. As long as T > 0K.
     
  5. Nov 9, 2018 #4
    The ideal setup would be to only allow photon emission to carry the energy away, with photons being the only source of energy transferred out of the material. I am not familiar with block body emission.
     
  6. Nov 9, 2018 #5

    Dale

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    Do you mean “no energy transferred out of the material except by thermal radiation”?
     
  7. Nov 9, 2018 #6
    So, for as long as T>0K, it will emit. Any ideas on what that might be for visible light, or would it be the same? Thanks again.
     
  8. Nov 9, 2018 #7
    Hi Dale. Assume that thermal radiation is also contained, and I just want to measure the loss of energy through photon emission. Or can I not have one without the other? Thanks.
     
  9. Nov 9, 2018 #8
    Thermal radiation is just a fancy way to say photon emission in this case.
     
  10. Nov 9, 2018 #9

    Dale

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    Radiation is photon emission (or emission of other particles, but just photons in this case). Thermal radiation is photon emission that is based on an object’s temperature. It is also called black body radiation for historical and technical reasons.
     
  11. Nov 9, 2018 #10
    Cool beans, BearY. It's only a hypothetical query at this point, as my focus is on researching various materials and their insulating and conductive properties. I like to invent stuff. But I like to research to see what can be done and what can't, and to push the limits as far as I can. :)
     
  12. Nov 9, 2018 #11
    Dale, if I wanted to separate the thermal mechanism from the photonic, whereby the heat was not transferred but the photons were, could that be done? Or would I have to go a different route other than heating a material? Thanks.
     
  13. Nov 9, 2018 #12

    Dale

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    Ok so we heat 1 cubic cm of steel to white hot, no conduction or convection so the only energy transfer is due to emission of thermal photons. And you want to know how long it will continue to glow in the visible spectrum, correct?

    What temperature is the environment?
     
  14. Nov 9, 2018 #13
    My background is pretty much computer aided drafting. I took intermediate physics way back in college, but forgot the stuff I never use lol, so thanks for putting up with the questions. :)

    Ideally, the molten steel would be enclosed, say, in a soda lime glass container as an inner shell, separated magnetically from an outer shell, and the space between the shells is a vacuum to prevent as much transfer as possible to where you would be able to touch it and it would feel cool. The surrounding environment outside of that would be regulated at 72dF, my favorite temperature. How long would it continue to glow? Thanks.
     
  15. Nov 9, 2018 #14

    gneill

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    If something is actually "white hot", would that not correspond to the temperature of the Sun's surface? About 5500 C? Steel melts at something like 1370 C. Iron boils at 2870 C. Methinks there will be a containment problem for more than heat conduction.
     
  16. Nov 9, 2018 #15
  17. Nov 9, 2018 #16
    Containment problem for sure :)
     
  18. Nov 9, 2018 #17

    russ_watters

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    We can do a specific scenario like @Dale proposes, but FYI, for objects that hot the vast majority of their heat loss is due to thermal radiation anyway. So we don't need to pretend we can insulate it from conduction and convection (though we could say it's in space...).
     
  19. Nov 9, 2018 #18

    gneill

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  20. Nov 9, 2018 #19
    Hi Russ. Ok, so it would continue emitting photons until its thermal energy is dissipated. How long would it continue to glow in the visible spectrum before going dark? Thanks.
     
  21. Nov 9, 2018 #20
    Hopping off here. Have to get up early. Thanks very much for all the replies and help guys, and keep it coming. My original thought was like a desktop paperweight or fancy gift item that is transparent with a white hot drop of steel at its center. Later on. :)
     
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