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Does the photon wavelenght come back to original when one path is blocked ?

  1. Feb 8, 2010 #1
    does the photon wavelenght come back to original when one path is "blocked"?

    Subject: Single particle (photon) interference in double slit or half silvered mirror experiment....question about wavelenght and phase shifts...

    in the half silvered mirror experiment or the double slit experiment with single photon .....

    when the photon passed through the half silvered mirror...its wavelenght gets halved (depending upon the angle of the mirror and lenght of path)...if i understood this correctly...

    and later...when both the paths are make to combine ...the photon interferes with "itself"...


    my question is:

    if one of the paths is blocked....does the photon get back (keep) its original wavelength?

    and of course this would work for delayed choice experiment also?
     
  2. jcsd
  3. Feb 8, 2010 #2

    Cthugha

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    Re: does the photon wavelenght come back to original when one path is "blocked"?

    No. It does not. The wavelength does not change at any time in common double slit experiments. If it did, that would cause a violation of conservation of energy.
     
  4. Feb 8, 2010 #3
    Re: does the photon wavelenght come back to original when one path is "blocked"?

    however there is a phase shift...

    does the phase shift come back too? if the other path is blocked?
     
  5. Feb 8, 2010 #4
  6. Feb 8, 2010 #5

    Cthugha

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    Re: does the photon wavelenght come back to original when one path is "blocked"?

    Yes, there is a phase shift in the light field each time the light is reflected off a mirror. If both arms of the interferometer are open, you will therefore create a phase difference between both arms and of course also between the exit ports of the final beam splitter, which can create destructive or constructive interferences at the detectors.

    If you now block one of the arms, there is only the field of one path left "feeding" the final beam splitter and of course there can be no phase differences as you have only one field left. Note that phase is NOT a property of the photon, but of the underlying field.
     
  7. Feb 8, 2010 #6
    Re: does the photon wavelenght come back to original when one path is "blocked"?

    however of course ...would there still be a phase shift in the photon's wavelenght pre and post reflection? when the other path is blocked...
     
  8. Feb 9, 2010 #7

    Cthugha

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    Re: does the photon wavelenght come back to original when one path is "blocked"?

    A phase shift in the wavelength? That does not make sense. Phase and wavelength are two completely different properties of light fields. The only thing you can measure about phase are phase differences between two fields when they overlap. So when you block one of the beams, you have only one beam present and there will be no measureable phase difference between the field and itself. You can imagine that there will still be a phase shift due to reflection, but that is not measurable until you superpose this field with another field to test the relative phase between them. If you did that, you would see that the phase shift due to reflection remains the way it is inside one arm, no matter whether the other arm is blocked or not.
     
  9. Feb 9, 2010 #8
    Re: does the photon wavelenght come back to original when one path is "blocked"?

    i have posted a new thread on a different topic i.e. delayed choice.

    in case you are interested please take a look, i look forward to your reply
     
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