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Double slit experiment with macroscopic size objects

  1. Sep 17, 2006 #1
    Hi; I'm new to the forum and I hope my question is not out of line.

    Has anyone ever done double slit experiments with macroscopic objects such as grains of sand, for instance. It seems to me that with appropriately sized and spaced slits in a mask of appropriate thickness, one should be able to reproduce, in the detector (a gel for instance) a pattern that would resemble an interference pattern.

    The size of the grains of sand combined with the correct spacing and size of the slits in a mask of appropriate thickness should illustrate that some paths to the detector are possible while others are not, without the necessity of resorting to wave functions to describe the paths.

    I would guess that as the separation between the slits, the size of the slits and the thickness of the mask were altered, so too would the "interference" pattern change in the detector.
  2. jcsd
  3. Sep 17, 2006 #2
    The biggest thing they done with the double slit experiment was with buckey balls, which is a form of carbon, it is 60 carbon atoms big, which is pretty big in the atomic scale
  4. Sep 17, 2006 #3
    The whole point of the double slit experiment is that the interfering particles don't behave like grains of sand.

    Firstly, the quanta in the 'true' double slit experiment can follow all possible paths, unlike your sand hypothesis.

    Secondly, were you to observe a distribution pattern with the sand experiment, the greatest concentrations of sand would probably be approximately (amount of sand from slit 1) + (amount of sand from slit 2) - reasonable, no?

    It turns out that quantum interference patterns don't behave like this. Rather, the interference peaks are of the form (amount of 'stuff' from slit 1) x (amount of 'stuff' from slit 2). This is one of the important effects that the experiment is supposed to show.

    The double slit experiment is based on entirely different mathematics to this sand experiment, I'm afraid.
  5. Sep 17, 2006 #4
    The problem is that you need a coherent source: it's rather impossible to ensure that that in the case of sand grains.
  6. Sep 17, 2006 #5
    I don't think that's the issue here. We do see double slit interference for a thermal light source.

    Recalling De Broglie's relation, assuming a sand grain of mass 1mg and demanding a 1/2 mm wavelength (since I'm sceptical that a wavelength below the particle diameter will work), the sand would need a velocity of 10^-24 m/s. To emphasize the problem (via equipartition theorem) you're looking at maintaining 10^-31 K and (to propagate into a diffraction pattern) preventing any interaction for up to 10^14 centuries..

    You should look up the research on buckyball interference.
  7. Sep 19, 2006 #6


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    Buckyballs are indeed the reigning heavy weights in the double slit world. It is already plenty weird anything this big can submit to quantum effects. I think the 'double slit' effects occurs at all scales but is too tiny to be measurable at macroscopic scales. Sort of like trying to weigh an elephant to the nearest .001 gram.
  8. Sep 19, 2006 #7


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    Or the question they used to get back in the nineteenth century: "Is there diffraction around a chair?".
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