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Photon origins

  1. Dec 9, 2005 #1
    When a photon is emitted, where did it come from? Did something cause it to be created and then emitted, or was it inside something and then released? How's it work?
  2. jcsd
  3. Dec 9, 2005 #2


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    You could ask the same question this way: when kinetic energy appear when you let go of a ball, where did it come from?

    A photon is simply a clump of energy (with spin of 1). So it appears, naively, out of conservation of energy.

  4. Dec 10, 2005 #3
    A photon is a particle that is actually created. How its created will depend on the particular process.

  5. Dec 10, 2005 #4
    Perhaps when light (invisible and with no mass) reflects off of an object a photon(s) is (are) created.
  6. Dec 12, 2005 #5
    In my opinion light, coming from atomic de-excitation must come from a physical principle very closely related to that one which tells us that accelerated charge emitts radiation.
    Perhaps, in between two stable orbits, the "collapse" dynamics are very much the same as the one predicted by classical theory.

    Best Wishes

  7. Dec 12, 2005 #6


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    I don't quite agree to that. If you say that QED can describe both energy transition and charge acceleration in the production of photons, I agree. But if you claim that classical E&M theory can make a coherent explanation for light emission in energy transition, I haven't seen it.

    Remember that in an energy transition in an atom to emit photons, it isn't just a change in the principle quantum number "n" that produces an energy change. There is also a selection rule that requires a change of +- 1 in the orbital angular momentum. This accounts for the spin 1 that photons have and preserves conservation laws in a single transition.

  8. Dec 14, 2005 #7
    Dear Zz,

    I didn't say "classical E&M theory can make a coherent explanation for light emission in energy transition" but instead I said that, in my opinion, the photon's structure must have something of what is involved in the classical E&M explanation. Spin stuff is a nice argument of yours, and force me to take back my words and try another way to express my ideas.

    If the electromagnetic field can be thinked of as a depositary of angular momentum which came from the electronic-atomic decay you may agree with me that it is possible to understand it in terms of the forces that photon will make upon another charged entities located elsewhere in the universe.

    Do you agree with me in this point ?
  9. Dec 15, 2005 #8
    Its a common misconception of imagining a photon to something like a particle , or a point mass , a photon is infact a 'bundle-of-energy' , When you think about n number of photons striking a surface , think about much energy striking the surface.Photons represent the particle nature of light, which carry the energy in paryicle-sense , analogous to wave carrying the wave-energy in wave-nature sense.

  10. Apr 19, 2011 #9
    but what if you thing of light as a wave, the thwory states that a photon is both a particle and a wave
  11. Apr 19, 2011 #10
    Hmmm... this is a nearly 6-year old thread.
  12. Apr 19, 2011 #11


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    Photons have both particle and wavelike properties which are explained by Quantum Mechanics.
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