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Photons from Electons?

  1. Oct 29, 2006 #1
    When you thermally excite an electron to a higher energy level, it quicky comes back to its ground state by realeasing its energy in the form of a photon(s).

    We all, I assume, accept this fact. But does it make sense? How does the electron do that? I thought that the electron was an indivisible particle without any volume. Then how can it emit a photon?

    Is this something that is left unexplained by physicists?
  2. jcsd
  3. Oct 29, 2006 #2
    According to the theory of Quantum Electrodynamics, the electron (field) is coupled to the electromagnetic field. An excited electron will cause the electromagnetic field to become wiggly, and these wiggles will travel away from the atom at the speed of light (as per Maxwells equations). These wiggles are to be interpreted as photons. The electron will no longer be excited.

    Analogy: Imagine you get onto a trampoline, and you stand atop it steadily. If you represent the electron and the trampoline represents the electromagnetic field, this scenario corresponds to the atom in the ground state (electron is not excited).

    Now jump (exactly once) on the trampoline. Your jumping motion represents the excited electron. If you imagine yourself jumping on an infinitely large trampoline, you should be able to convince yourself that your subsequent bounces will diminish in amplitude, as the trampoline saps energy from you. The wiggles that you create on the trampoline represent the emitted photon.

    Disclaimer: This is an extremely crude picture of what goes on. The proper quantum mechanical description of this event requires the electron-proton system interacting with the quantized electromagnetic field (for spontaneous emission).
  4. Oct 30, 2006 #3
    I think that in a recent post someone else asked this question. The easy answer, as I recall, is that the atom (which includes the electron) is excited, and so the atom actually is responsible for the photon's emission.
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