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The enigma of the photon.

  1. Nov 3, 2009 #1
    What is the photon? Does it have a three dimensional shape? Why does it have an electric and magnetic component? Do these components give it a relationship to the electron and anti-electron? It must since the 1997 Stanford linear accelerator experiment of colliding energy beams created an electron and positron.
     
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  3. Nov 3, 2009 #2
    Whenever two electric charges get very close together, virtual positrons and electrons are created in the Coulomb field. This is known as vacuum polarization, and is part of charge renormalization. In high energy electron-electron or electron-positron collisions, there is more than enough energy to create real electron positron pairs. SLAC has created 1-miiliamp positron beams using pair production. SLAC has even created electron-positron pairs by shooting a laser at an electron beam, which gamma-boosts the laser photons by a factor of about gamma-squared.
    [added] Early experiments that first verified(?) the quantum nature of the photon included the photoelectric effect, and also about the transverse electric field (by polarization of the electron recoil), and later by verification of the theoretical prediction of the cross-section and magnitude of polarization effects in Compton scattering, bremsstrahlung, pair production, etc.. For a thorough review, read Heitler's book on the Quantum Theory of Radiation.
    Bob S
     
    Last edited: Nov 3, 2009
  4. Nov 3, 2009 #3

    DrChinese

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    Photons, like all quantum particles, have both a wave character and a particle character. They do not, of themselves, have an electric/magnetic component but they do participate, as Bob_S says, in virtual exchanges between charged particles.

    It is a bit hard to answer this question in much detail without you being more specific. Have you already looked in Wikipedia and similar? Are you familiar with QM concepts such as the HUP? It's OK if you aren't but it would help in formulating a useful answer for you.
     
  5. Nov 3, 2009 #4
    But photon can fly on the photon if they not polarized, but even polarized at point intersects like magnetic and electric fields intersects in 3 variants: magnetic and magnetic, electric and electric and magnetic with electric and infinity photons can be in limited space (and on each over), which nicely match with manywords interpretation.
     
  6. Nov 3, 2009 #5
    I am relatively familiar with the concepts of QM and how it deals with electromagnetic energy via virtual particles. Einstein once said if we understand the Universe we can explain it to almost anyone. I have difficulty understanding how we could invent a particle that no one has ever seen nor will they ever see or prove it's existence and then decide there is no need to look any further for a description of the photon. Just because the tool we have invented adequately describes the phenomena does not mean we fully understand it.
     
  7. Nov 3, 2009 #6

    DrChinese

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    Not sure exactly what you mean by "no one has ever seen nor will they ever see or prove it's existence". EVERYTHING we see is the result of the photon's transmission from the object to our eye. As to the existence of photons, that has been proven in many many ways. Just really is a function of what it takes to convince you, some people cannot be convinced regardless of the evidence. Are you one of those?

    As to fully understanding... again this is a function of what you might define as "understanding". If I have a complete description of something, is that understanding? How would I have full understanding without a complete description? Some of this is semantics, which would be beyond the scope of any answer I might supply.
     
  8. Nov 3, 2009 #7
    I was referring to the virtual particles used to explain the interaction of light with matter and lights propagation. My point is that we do not understand what is waving about light. Is it space that is waving or maybe time itself? Is there some geometric shape to light? If so how would this geometric shape be changed into matter. For us to understand matter we must fully understand light first.
     
  9. Nov 3, 2009 #8
    We don't need to know about virtual particles to explain photon interactions all the way from the photoelectric effect to the Thomsen and Compton cross sections to bremsstrahlung (below 1 MeV). Even virtual pair production was understood since 1935 or so. See paper by Uehling in Phys Rev:

    http://prola.aps.org/abstract/PR/v48/i1/p55_1

    Bob S
     
    Last edited: Nov 3, 2009
  10. Nov 8, 2009 #9
    In a classical sense it is an electromagnetic wave determining the electromagnetic force in a probe charge equations. An experimental fact.

    In a quantum sense it is an electromagnetic wave of the smallest amplitude for a given frequency.
     
    Last edited: Nov 8, 2009
  11. Nov 8, 2009 #10

    RUTA

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  12. Nov 8, 2009 #11
    Rubbish! In a dusty air we see the photon flux travelling through and scattering from dust.
     
  13. Nov 8, 2009 #12
    The dust particles are the detectors. What do you see between the source and the dust particle?
     
  14. Nov 8, 2009 #13
    Bob, you bring up an interesting point. What is amplitude in relation to the photon?
     
  15. Nov 8, 2009 #14
    A photon amplitude is determined with its frequency and the volume where this photon propagates. It is not an interesting point per se. The main idea is that for two coherent photons the amplitude doubles. So the classical electromagnetic wave is a flux of coherent photons.
     
  16. Nov 8, 2009 #15
    Wrong, the dust particles are scatterers (secondary sources) and my eyes are detectors.
    Between the source and the dust particles I see a free-of-dust space where the waves propagate.

    And how about optic wave-guides? They do guide photons, don't they?
     
    Last edited: Nov 8, 2009
  17. Nov 8, 2009 #16

    RUTA

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    The scattering dust particles are detectors for the original source and sources for your eyes (at least for the photons your eyes absorb). Zeilinger's ontology is absolutely valid.
     
  18. Nov 8, 2009 #17
    Oh yes! We can go father and say: "I feel nothing but my own feelings". What a science can we build from that?
     
  19. Nov 8, 2009 #18

    RUTA

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    I think Zeilinger does quite well with his view actually.
     
  20. Nov 8, 2009 #19
    Good for him!
     
  21. Nov 9, 2009 #20
    Does the energy of two coherent photons double?
     
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