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Double Slit Experiment, Testing the Test

  1. Jan 2, 2014 #1
    Something I've wondered about the Double Slit Experiment is what happens to photons which fail to pass through either slit, and what is their behavior?

    Why not put some detectors on the source side of the slits during a double slit experiment to try to determine whether the photons are behaving like a particle or wave even before they reach the slits? For example, will the photon be found to be "interfering with itself" or alternating particle/wave properties even before it reaches the slits?

    To test this, I was thinking of putting detectors between the two slits, above, below, and on either side of them in order to find out if the photons, or anything else, hits the source side of the obstacle during the experiment.
  2. jcsd
  3. Jan 2, 2014 #2
    The photons which do not pass the slits are absorbed by the slit plate, the same as if there were no slits in the plate.
    Photons behave partly as particle and partly as wave. The wave determines the probability of absorption, and before the slit the wave is just spherical
  4. Jan 2, 2014 #3


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    The photons that don't go through the slits are either absorbed or reflected by the material that the obstacle is made of. Increase the intensity of the incoming light enough, and I guarantee that you will melt or burn up the obstacle, regardless of whether it has slits cut in it or not.
  5. Jan 2, 2014 #4
    I thought as much, however it is often claimed that the experiments are done by releasing one photon at a time. Am I to understand that these photons miss as well?

    Why would they miss if they are all aimed in the same direction?
  6. Jan 2, 2014 #5


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    You are missing the point. The single-photon idea means that at any given time, only one photon is inside or within the system. It has nothing to do with what was missed and what wasn't. The photon that didn't make it is not part of the experiment. All we care about is that the photon that made it in, there aren't any other at the same time to trigger the detector.

  7. Jan 2, 2014 #6
    I think that is a good point. It would suggest a sort of pre-selection. How do we calculate the effect of that on the results?
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