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Electron position in transparent materials and bit more

  1. Jun 7, 2009 #1

    Edi

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    So, i was thinking about this and figured out this: depending on electron orbit and, corespondingly, speed around the nuclei and energy of the photon, if the electron makes full cycle by the time it re-emits that photon the material is reflective - electron is in the same position where it absorbed it, so the photon is emitted in the same side.
    If the electron is in the other side of nuclei the photon is emitted in the other side, so the material is transparent. True, false?

    2. What exactly happens when photon is absorbed- its energy is transfered to heat/ motion of atoms?

    3. Atoms in a material with temperature >0K move around/ vibrate. Why doesn't this make chaos and prevent ,say, transparency by changing the rotation of the atom with the electron, so the electron isn't in where it should be? Or maybe the atom is something like a little gyroscope?

    I am new to this forum and started to really be interested in how stuff works and to search up info about ... everything about 2 years ago. (I am 17 now) So don't be too harsh on me, because there is a LOT of things i don't understand and i am just learning... ;)
     
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  3. Jun 7, 2009 #2

    ZapperZ

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    Please start by reading the FAQ thread in the General Physics forum, especially the entry on the photons going through a material. You have a few error in concepts here. In a solid, the "atomic behavior" is no longer relevant in most properties of a solid - that's why atomic/molecular physics is a different field of study than solid state/condensed matter physics. A solid has a collective behavior that is missing in an isolated atom.

    Zz.
     
  4. Jun 7, 2009 #3
    There are several ways photons can interact with atoms. This includes photoelectric effect, Compton scattering, pair production, bremsstrahlung, photonuclear reactions, etc. One you might be interested in is the photoelectric effect, in which all the energy of the incident photon is converted to potential and kinetic energy of a bound electron. The attached plot shows the probability (or cross section) on the vertical axis for a photon interacting with a lead atom, plotted against the photon energy on the horizontal axis. The probability is dropping very fast vs. photon energy in the 50 KeV range, but when it reaches ~80 KeV, the probability suddenly jumps up by a factor of ~5. The reason for the sudden jump is that when the photon reaches the binding energy of the innermost electrons in the K (or n=1) shell, the photon has enough energy to knock that electron out, so the probability of the photon interacting with the atom jumps up by a large factor. This is called the photoelectric effect. It can occur in solids, liqiuds, and gases. This can happen whenever the photon has enough energy to knock any electron off the atom, even if the binding energy is a few electron volts (visible light, etc.)
     

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    Last edited: Jun 7, 2009
  5. Jun 7, 2009 #4

    ZapperZ

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    Actually, that is called "core-level photoemission". It is nothing like the photoelectric effect that most people are familiar with, and certainly NOT the same type that is described using the Einstein equation. That equation doesn't work that well when we go beyond photoemission in a standard metal's conduction band.

    You need to be more careful what you are doing and not give misleading information here.

    Zz.
     
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