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Can Visible Light Produce Heat When Absorbed?

  1. Mar 26, 2013 #1
    "dark materials absorb more thermal energy than lighter colored materials"

    Initially I thought this statement was very straight forward and obvious.... then someone mentioned that visible light photons do not produce heat when absorbed and that IR was the only component that would be translated into heat. This seems to be very counter intuitive to me

    Here's my question:

    Say I had a flat, smooth layer of some material that happened to be colored black. Say this material is very absorptive of all visible light frequencies.

    If I was able to expose this material to an energy source that only generated visible light (400-700nm) would this material rise in temperature?

    If yes, what is the mechanism that converts the photons into heat?

    If not, then why would color even matter since all absorption/reflection of the heat producing frequencies occur in IR (or UV)?


    Thanks for any clarification you can provide
     
    Last edited: Mar 26, 2013
  2. jcsd
  3. Mar 26, 2013 #2

    mfb

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    Usually, they do. There are some exceptions (like photovoltaic cells), where the energy is used in different ways.
    It would.
    Absorption, leading to motion of atoms/molecules.
     
  4. Mar 26, 2013 #3

    Drakkith

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    Whoever told you that visible light doesn't produce heat upon absorption is 100% WRONG.
     
  5. Mar 26, 2013 #4

    CWatters

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    That's why it's black.
     
  6. Mar 26, 2013 #5

    Chestermiller

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    The primary mechanism for heating of the atmosphere is by ozone absorption in the visible.
     
  7. Mar 26, 2013 #6

    Drakkith

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  8. Mar 26, 2013 #7
    mfb, thanks for your response. From my understanding, the visible light is absorbed by the electrons which drives them into a higher orbital state. Do you know of any references on which I can read up on how these electrons then convert their energy into atomic motion leading to heat.
     
  9. Mar 27, 2013 #8

    Drakkith

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    Actually much of the light is absorbed by the atoms/molecule as a whole and converted directly into thermal motion. Unless the light is exactly the right frequency, an electron will not absorb it and jump to a higher energy orbital.
     
  10. Mar 27, 2013 #9

    Chestermiller

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    Sorry. I meant to say "heating from solar radiation in the visible." Heat from the ground is absorbed by the atmosphere in the IR and re-radiated back into space so that the net heating rate of the earth is zero (at steady state), assuming no anthropogenic perturbations.
     
  11. Mar 27, 2013 #10

    ZapperZ

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    Please note that, since we are talking about "material" (per your first post), this implies things such as solids. For the energy scale we are talking about, the property that we are dealing with are not "atomic orbitals", but rather a collective behavior of many, many atoms that have formed that solid. A isolated Cu atom has discrete energy levels, whereas the Cu wire that you are familiar with is a solid that has energy bands which are not found in individual Cu atoms.

    So when you are dealing with "materials", the interaction of visible light with that material are governs by the collective behavior, not by individual atoms in that material. The light could easily be absorbed by the lattice ions, causing an increase in lattice ions vibrations.

    So moral of the story here is that, if you learn that atoms in solids to not behave the same the same way as when they are individually isolated, then you have learned something.

    Zz.
     
  12. Mar 27, 2013 #11

    Drakkith

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    Not sure what you mean here. The ground transfers heat to the atmosphere mostly through physical contact. At the top of the atmosphere the heat can radiate away as IR, cooling the planet. Is that what you were saying?
     
  13. Mar 27, 2013 #12

    Chestermiller

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    No. The way you describe it is not how it works. See the following paper:

    Owens, A. J., Hales, C. H., Filkin, D. L., Miller, C. Steed, J. M., and Jesson, J. P., A Coupled One-Dimensional Radiative-Convective, Chemistry_Transport Model of the Atmosphere, 1. Model Structure and Steady State Perturbation Calculations, Journal of Geophysical Research, Vol. 90, No. D1, Pages 2283-2311, February, 20, 1985.
     
  14. Mar 27, 2013 #13

    russ_watters

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    Your posts are confusing to me, so lets just look at the numbers:

    [​IMG]
     
  15. Mar 27, 2013 #14

    Drakkith

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    Can't find a link that I can use. Mind explaining the process?
     
  16. Mar 30, 2013 #15

    Chestermiller

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    Mechanistically, cooling of the atmosphere occurs by radiation transport in the IR. Part of the IR flux from the surface is absorbed by greenhouse gases in the atmosphere, as described by Beer's law. The absorption occurs primarily in band structure of the gases. In addition, each parcel of air, based on its temperature, emits radiation to the surrounding parcels. This radiation is also absorbed by the surrounding parcels, as described by Beer's law. So there is a constant process of radiation and reabsorption. In the troposphere, thermal energy is also transferred by convection and water condensation processes. There is also radiation exchange with clouds in the troposphere. But, in the stratosphere, the primary cooling mechanism is radiation transport.
     
  17. Mar 30, 2013 #16

    ZapperZ

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    We need to get back on topic. The OP's question is much simpler than this. You guys are now adding factors that just create confusion.

    Zz.
     
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