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Question regarding the double slit experiment

  1. May 29, 2015 #1
    I'm just a layman with an interest in science, so my terminology won't be accurate. Sorry.

    Set up for question: the wave-front splits as it passes through the slits and must (I guess?) condense to a point upon impact with the recording device (paper/film etc).

    The question: if a photon is given to behave as a wave until it contacts matter, and thereupon condenses to a particle, why doesn't the wave condense when part of it strikes the barrier through which the slits are cut?

    Also, if you cut slits in the recording paper is the process repeated through a second iteration (albeit at a diminished intensity)?

    Thinking about this experiment is driving me insane. A logical explanation seems always just out of reach. Thanks in advance for any light you can shed on this for me.
  2. jcsd
  3. May 29, 2015 #2
    Wrong guess. It is a wave in the sense that the probability distribution for finding the point-like particle evolves in the same manner as a wave front, including the interference with the other wave front: the recording device registers a particle in accordance with the modeled probability distribution. There's no condensing.
  4. May 29, 2015 #3
    So there is no wave per se? Only a wave-like probability distribution for the changing particle position?
  5. May 29, 2015 #4
    Yes. Of course, that rules out the projectile-like particle model as well. We call them "particles" because they have a discrete point-like quality at the detectors. Neither "wave" or "particle" would be an appropriate term if referring to their daily life counterparts.
  6. May 29, 2015 #5
    Ok, thanks. Does that mean that a large percentage of the photon emissions don't strike the recording apparatus at all, having struck the barrier instead of passing through a slit?
  7. May 29, 2015 #6
    Yes, they have been absorbed or reflected by the barrier's material. Note however that you can emit one photon at a time, and no matter the rate (you could emit one photon per year if you wanted to) the photons that do pass through the barrier will still form the diffraction pattern when enough events have been collected. So the probability wavefunction model associates a whole probability wave pattern, in this case complete with multiple fronts (for n slits), to each singular photon.
  8. May 29, 2015 #7
    Yes. A second interefence pattern could be observed on a second screen beyond the first.

    If you want to take this further, it's worth understanding how this depends upon slit placement.
    Last edited: May 29, 2015
  9. May 29, 2015 #8
    Thanks ddd123 and craigi.
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