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Question about electron slit experiments

  1. Jan 23, 2014 #1
    First I want to admit that I'm not a physicist, but I'm very interested in physics. I have some questions about quantum mechanism that I haven't been able to find the answer through prolonged internet search, and I registered this site just to get answers to these questions.

    One of my question is regarding the electron slit experiment (or photon slit experiment alike). Online literature says that such experiment had been conducted that the electron pass through the slits one by one. My question is about the specifics of the experiments: Does every single electron shoot out of the electron gun go through the slit and form a dot at the backstop, or only some of them make it though? I think the answer is most likely no, but I'm not sure.
    Last edited: Jan 23, 2014
  2. jcsd
  3. Jan 23, 2014 #2


    Staff: Mentor

    In both experiments most in fact hit the screen - only some pass through the slits.

    I can guess what your next question will be but wont pre-empt it.

  4. Jan 24, 2014 #3
    Thanks for the answer. Actually, I don't have a definite follow up question in mind. But I do like to here what you think my follow up question is.

    My main interest is in interpretation of uncertainty principle. I had had the idea that quantum mechanism can be explained by introduction of hidden variable. But by some recent reading, I realized that that possibility is mostly ruled out.

    Another question that I'm quite interested in is what account for "measurement". Is it true that any kind of interaction between things is a measurement? For example, what about the electron and Proton in hydrogen atom? Is their interaction considered measurement? Does the macro world look deterministic because we are observing the collapsed quantum reality?
    Last edited: Jan 24, 2014
  5. Jan 24, 2014 #4


    Staff: Mentor

    The question I thought you would ask is what determines which electrons hit the screen and which goes through the slits. The answer is the screen constitutes a position observational apparatus of the filtering type ie after the screen the photon or electron is in a superposition of the position of the slits.

    These days measurement is generally associated with decoherence:
    http://www.ipod.org.uk/reality/reality_decoherence.asp [Broken]

    Last edited by a moderator: May 6, 2017
  6. Jan 24, 2014 #5
    Another question regarding the slit experiment: After an electron pass through the slits and form a dot on the backstop. So what happened when it hit the backstop? since we can be relatively accurate about it's position at that moment (do we?), is it true that it's momentum become uncertain?
  7. Jan 24, 2014 #6


    Staff: Mentor

    When it hits the screen its destroyed and leaves a mark indicating the position it was destroyed. You cant really speak of momentum for something that doesn't exist.

    However for the photons/electrons that go through the slit its momentum is largely uncertain.

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