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What is it about the EM waves that get absorbed by electrons

  1. May 1, 2016 #1
    What is it about the em waves that get absorbed by electrons compared to em waves that traverse solid material.What is it about that wavelength, or frequency of light, and other em waves that get absorbed by electrons, that makes visible light get absorbed by electrons.
    Why that specific wavelength, and frequency in certain em waves, that gets absorbed by electrons.
    I am thankful for your help, anything helps even a few words.
  2. jcsd
  3. May 1, 2016 #2

    Simon Bridge

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    EM waves are not absorbed by electrons - it sounds like you are conflating two different models.
    There is nothing special about the light that gets absorbed and the light that passes through materials ... it's the same light.
    What makes the difference is the materials.

    The specific wavelength depends on the specific arrangement of charges/atoms/molecules in the material.
  4. May 2, 2016 #3


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    It has to do with the amount of energy per photon of the EM wave vs the available energy levels in the material. When absorbing energy from an EM wave, a material can undergo an electron transition, which is the change in an electron's energy level, or one of several transitions associated with transverse, rotational, or vibrational motion of the molecules making up the material. For a transparent material, the energy of visible light does not match up with any of the energy levels available to the material, so the light is not absorbed.

    By this do you mean that an EM wave is absorbed by the molecule or material as a whole and not simply the electrons themselves?
  5. May 3, 2016 #4
    Great, thank you

  6. May 3, 2016 #5
    Hi, Drakith,
    I meant the absorption, and emission process of light, compared to radio waves that traverse a solid material.
    I am grateful for any help.
  7. May 3, 2016 #6


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    That's not true in general - metal sheet will stop radio waves.

    And actually the physics behind the metal sheet stopping radio waves is exactly the same one that is responsible for the glass being transparent. Google "band theory of solids".
  8. May 3, 2016 #7
    Dear, Drakith thanks for your help, I think this is the best forum for answers on the internet.
    There is so many ways to play around with em waves, increasing wavelength, and frequency, combining invisible em waves together as a intertwined ray, and also heating, and cooling the material, to help absorb, or transmission the em waves.
    I think there is a right balance of invisible em waves if mixed together into a single beam, and the material that the em waves passed through was heated up, or cooled down to affect absorption, and transmission.
    It could be possible to raise electrons in a material to the same energy levels of glass, to make the material translucent, or transparent, by a certain percentage.
    The em waves have be finely tuned to perfection, when mixed to find the right wavelength, with the right frequency.
    IF the frequency could be adjusted with the right wavelength, it could make em waves that traverse, yo then absorb WHILE inside the material the em waves pass through.
    What do you think, could it be done.
  9. May 4, 2016 #8


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    It's not clear what you are trying to do. Do you have a reference to where you have read something like this? Just adding EM waves does not do anything special. You need to use non-linear effects when adding two strong EM beams to get anything unusual to happen (like optical mixing)...

  10. May 11, 2016 #9
    Metal and glass have different mechanisms of absorption.
    Your "models" seem to be just based on atomic absorption. In solids the things are a lot more complicated. Not that atoms are simple.
    You should study energy bands in solids.

    In a metal you have free electrons and optical absorption is due to them mainly. The energy levels in the conduction band is almost continuous and the frequency of light absorbed is not related to some energy difference between energy levels, as in atoms.
    Heating up the metal has a very minute effect of the conduction electrons. They are already "very hot". Look up Fermi temperature.

    Glass and ionic crystals are quite different. You may have absorption on lattice vibrations. (see optical phonon modes).
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