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Electromagnetic radiation is the acceleration or deceleration

  1. Jun 24, 2005 #1
    the source of all electromagnetic radiation is the acceleration or deceleration of charged particles, mostly electrons….only when an electron jumps down energy levels, a photon/ electromagnetic wave is emitted…sounds contradicting to me, how can be both correct?

    Hope question isn’t too silly.
  2. jcsd
  3. Jun 24, 2005 #2
    When electrons are jumping up and down energy levels they're bound to atoms. In the other scenario you have free particles. There's no contradiction.
  4. Jun 24, 2005 #3


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    The energy spectrum for the free electron is continuous,while for the bounded one is discrete.

  5. Jun 24, 2005 #4
    Thank you, that makes sense.

    Are the photons emitted and absorbed by free electrons then virtual photons?
  6. Jun 24, 2005 #5


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    What do you mean by "then virtual photons"?It's all about reading correctly a Feynman diagram.

  7. Jun 24, 2005 #6
    Well, there is where the problem starts, I have no clear idea of what virtual particles are, only heard that all forces work by exchanging bosons which are virtual and that these virtual carrier particles only exist during this exchange process.

    I remember also reading somewhere that free electrons don't have the energy (as opposed to bound electrons) to emit real photons, but according to time/energy uncertainty every free (and accelerating?) electron emits and absorbs virtual photons.

    But I believe I confused a lot. Could you help me out?
  8. Jun 24, 2005 #7
    First Phenomena

    Electron at rest has an electric field, when in uniform motion, has constant magnetic field at a point,when accelerating has a changing magnetic field, and as a changing magnetic field induces a changing electric field,therefore an accelerating electron forms an electromagnetic wave.

    Second Phenomena

    When an electron jumps from one energy level to another , the difference in energy levels is emitted as a radiation of same electromagnetic wave of the same energy.
  9. Jun 24, 2005 #8
    well, you need to conserve Energy-impulse, that is why one free electron cannot emit one free photon. Then orbital momentum, electron charge, and some other stuff should be consserved as well, that is why electron cannot emit two photons (not sure about that, but an inquiring person could find this out relatively straigforwardly).
    As to virtual particles, they say that an enery uncertanity allows to emit a photon for a short time, but it should be reabsorbed for the conservation laws to hold.
  10. Jun 25, 2005 #9
    Much thanks so far. Could someone talk about free electrons and virtual photons a little bit more.
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