In experiments it is easy to discern between 2 and more-than-2 fringes on a screen, making the double-slit experiment the default one for wave-particle tests.

Let's say we shoot massive particles (e.g. electrons) towards a slit. Would the image behind it be the same no matter if we consider the electrons to be classical particles or wave-packets?

My interpretation, using an ideal (infinitely-narrow) slit, is that the (interpretation of the particles as) classical particles would produce an image with sharp boundaries, while a wave would imprint a gaussian-like distribution on the screen.

  • $\begingroup$ I agree with your last paragraph, except the pattern would not be gaussian. Essentially the slit would act as a line source of radiation. $\endgroup$ Aug 2, 2015 at 17:07
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    $\begingroup$ Might be helpful: what-is-a-wavelength-of-an-em-wave-physically $\endgroup$
    – gox
    Aug 2, 2015 at 22:29

1 Answer 1


There is still interference at a single slit resulting in a Fraunhofer pattern. Just consider both edges of the split as starting point of a new wave.

Generally you're right. But, in a single slit, the electrons could still be deflected by the atoms that make up the slit. This - I think - leaves more room for discussion than the double-slit. It is propably just a matter of what resonated with people first and would gives students the least amount of headaches..

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    $\begingroup$ You're right, but I think it is best to think of an ideal slit, not a messy one with particles at the edges. With an ideal slit you get the interference pattern, and the more narrow the slit is, the wider the pattern. $\endgroup$ Aug 2, 2015 at 17:04
  • $\begingroup$ In that case the electrons would be deflected by the atoms at the edges also in the double slit experiment. As Mike said, let's consider an ideal slit. Anyway, that was an example, I'm talking about massive particles in general. Now for buckyballs, isn't it practically easier to work with only one slit rather than two of them? $\endgroup$
    – Rol
    Aug 3, 2015 at 6:15
  • $\begingroup$ A buckyball is still rather small compared to macroscopic distances and is in most situations seen as a quantum dot. $\endgroup$
    – t0xic
    Aug 5, 2015 at 18:39

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