Say we have a double slit experiment. Besides the slit width, separation and distance from the detection screen, the color of light determines the fringe pattern spacing's. So red and blue have different patterns. Now if you take the same exact double slit experiment and fire electrons what determines the wavelength or pattern?

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    $\begingroup$ Bill, the velocity of the electrons as well as the electric potential of the slit influence the intensity distribution on the observers screen. Historical facts about electron deflection at edges see my elaboration academia.edu/27983554/Deflection_of_electron_beams_at_edges $\endgroup$ Sep 16, 2016 at 17:54
  • $\begingroup$ @HolgerFiedler thanks I assumed it had something to do with that but wasn't sure. So really there are a lot of variables? Depending on the Electron speed The emitted photons could be any frequency? Could the frequency be so high that the pattern is hard to see? Could multiple electron impacts vary to the point that frequencies mixed and destroyed the pattern? Is there an an article or paper on this particular subject? $\endgroup$ Sep 16, 2016 at 18:08
  • $\begingroup$ Why do you think that a moving electron has to emit photons? BTW the impact on the observers screen is really an electron and not from photons. $\endgroup$ Sep 16, 2016 at 18:40
  • $\begingroup$ I don't think moving electrons emit photons. I only think accelerated electrons do. Either when they bump the slit edges or impact the screen. I realize the impacts are made by electrons but I'm suggesting they're being guided by the unseen photon pattern. That's the reason for my original question what determines the frequency that also determines the pattern? $\endgroup$ Sep 16, 2016 at 18:46

1 Answer 1


"the color of light determines the fringe pattern spacing"

Not the color, the wavelength. Yes, these ideas are coupled, but if you perform the experiment in a medium of non-trivial index of refraction, the fringes shift.1

And that tells you the property to use for particle version of the experiment: the de Broglie wavelength.

(You can also deduce this from how the interference develops: the two path from slit to screen cover different distances.)

1 This is roughly how gas indexes of refraction are measured, though they use a more powerful interferometer than a simple pair of slits.

  • $\begingroup$ Yes I realize it's not the color but I would also say it's more the frequency. So ultimately it comes down to slit width, slit separation, number of slits and and the wavelength or frequency. So if The experiment is set and we fire electrons at it what determines the wavelength or frequency? $\endgroup$ Sep 16, 2016 at 19:38
  • $\begingroup$ No, it is not the frequency. It is the wavelength. The frequency doesn't change in a material medium and the wavelength does. Putting the experiment in a material medium shifts the fringes. It is very easy to get the idea that the two notions are interchangable (coupled as they are by the speed of light), but in some cases it is clear which one rules. This is such a case. $\endgroup$ Sep 16, 2016 at 19:40
  • $\begingroup$ What is the medium you speak of? The slits? The screen? $\endgroup$ Sep 16, 2016 at 19:41
  • $\begingroup$ You take the whole apparatus and dunk it in a water tank. Or just pressurize the air in the room. $\endgroup$ Sep 16, 2016 at 19:42
  • $\begingroup$ I'm talking about in a vacuum where only slits, detection screen, electrons and randomly emitted photons are involved. $\endgroup$ Sep 16, 2016 at 19:44

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