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Young's Double Slit experiment

  1. Jul 22, 2009 #1
    Hi all

    I have a doubt on this

    The experiment per se does not say anything wrt to the size of the slit right?

    Now my question here is, if i actually reduce the size of the slit to such a size that only one atom of a particular gas(say helium) can pass through this

    Now let us say i bombard the slits with helium and then shine light(laser if you like, of different phases) on it then, would the interference pattern still be observed, or will the light get blocked out?
  2. jcsd
  3. Jul 22, 2009 #2


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    There are issues about slit size and spacing. For there to be interference, there must be multiple paths without cancellation. There are a number of related issues.

    Assuming that: if you shine light incident such that the path taken can be determined, then the interference disappears.
  4. Jul 22, 2009 #3

    DrChinese just wanted to know, why is size never taken into account for this experiment, is it because it has never been repeated with other particles like electrons and with varying slit sizes. Seems a pity that such a nice experiment does not have enough data

    Why would the interference disappear if i shine laser beams, phase shifted wrt each other?
  5. Jul 23, 2009 #4


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    1. Interference has actually been demonstrated with all kinds of subatomic particles, including molecular nuclei (such as fullerene). So size been investigated. In fact, there is a web page that shows what happens when size parameters are varied, although I don't have the link in front of me.

    2. Any mechanism that allows the "which slit" information to be learned will cause the interference to disappear.
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