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Do photons collide with each other like any other massive object?

  1. Mar 20, 2008 #1
    If they do:
    -Do the collisions obey newton's law of motion.
    If they don't, why?
    What is the difference between a real particle and photon ?
    -We know that they both got mass ( photons have relativistic mass E/c^2).
    What is the significance of this mass? What does it imply?

    Any help will be highly appreciated. Thx
     
    Last edited: Mar 20, 2008
  2. jcsd
  3. Mar 20, 2008 #2

    pam

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    1. Photons obey the laws of relativistic quantum field theory, including photon-photon scattering.
    2. The photon is as real as any other particle, but has zero mass.
    3. Photons do not "have relativistic mass E/c^2". That is an archiac notion, inappropriate in relativistic quantum field theory.
    4. That mass has no significance. Its only implication is confusion.
     
  4. Mar 20, 2008 #3
    so it's possible that two electron collided and bounched off......
     
  5. Mar 20, 2008 #4
    by the way what do you mean by the word "other particle"? What is a particle?
     
  6. Mar 20, 2008 #5

    jtbell

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    Staff: Mentor

    "Photon collisions" have been discussed in a recent thread here:

    https://www.physicsforums.com/showthread.php?t=219619

    Photons are about as non-Newtonian as one can imagine. After all, they originated in quantum theory, and are fully described only in relativistic quantum field theory.
     
  7. Mar 21, 2008 #6
    A collision on a micro perspective are just forces bouncing eachother off. I dont think photons have any such forces which can make them bounce, otherwise it would be easily observed by letting two light rays cross eachother. Hence they only act like a superposition of waves when in the same space. Also according to pauli exclusion principles, there's no limit to how many photons may occupy the same state.
     
  8. Mar 22, 2008 #7

    jtbell

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    Staff: Mentor

    Photons can interact with each other via a process that involves virtual electrons and positrons. I included a diagram of it in this post in the thread that I referred to earlier. This process has a very small cross-section (probability) and is difficult to observe.
     
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