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B Destructive interference and conservation of momentum

  1. Jul 28, 2016 #1
    If two photons travelling in the same direction but out of phase cancel each other out, what happens to the energy and momentum?
     
  2. jcsd
  3. Jul 28, 2016 #2

    BvU

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    They do not cancel each other out.
    If they have a lot of energy, they can collide and form other particles (with the right quantum numbers). Energy and momentum are conserved.
     
  4. Jul 28, 2016 #3
    If they cancel in one region of space, they must enhance in other.
     
  5. Jul 28, 2016 #4

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    Who says 'they' cancel? What exactly cancels ?
     
  6. Jul 28, 2016 #5

    stevendaryl

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    I think the OP is thinking about interference of light, as is demonstrated by the two-slit experiment, for example. I would split his question up into three parts:
    1. Is it possible to arrange two sources of light so that you get total destructive interference? He seems to think the answer is "yes", but I'm pretty sure the answer is "no"; if the two sources interfere destructively in some regions, then they will interfere constructively in other regions.
    2. Assuming that the answer to the first question is "yes", does that imply that two photons can interfere so that there is zero probability of detecting any photon anywhere? I'm pretty sure the answer is "no".
    3. Assuming that the answer to the second question is "yes", how do you explain where the energy went?
    Since the answer to the first question is "no", the other two questions are moot.
     
  7. Jul 28, 2016 #6

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    OP ? What's your status now ?
     
  8. Jul 28, 2016 #7
    Stephendaryl covered it pretty well. Thanks for replying.
     
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