For the double-slit experiment, many websites and videos show models of the screen at the end that can determine the final measured position of individual photons, but I can't seem to find what the screen actually is.

Could someone please tell me what kind of detector/screen at the end of the two-slit experiment can detect individual photons positions?

Additionally, what kind of equipment can shoot individual photons?


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    $\begingroup$ Use your wall. See physics.stackexchange.com/a/266809/44126 $\endgroup$
    – rob
    Commented Dec 22, 2023 at 15:17
  • $\begingroup$ As is said in the question, I wish to know what detector/screen can be used to detect individual photons - which a 'wall' cannot do. $\endgroup$ Commented Dec 23, 2023 at 14:17
  • $\begingroup$ Did you mean detect individual photons one at a time or individual photons as a group? In any case the results are the same. In 1907 one at a time photons were detected using film .... in modern times we can use an EMCCD camera. IN all cases the final "screen" is either a camera/film/ or your retina. $\endgroup$ Commented Dec 23, 2023 at 14:38
  • $\begingroup$ I'm not quite sure what you mean? I wish to know what equipment is used to detect individual photons one at a time, and I don't think a camera/film/retina can do that. However, the EMCCD camera seems very helpful and exactly what I need, thank you, I'll look into that! $\endgroup$ Commented Dec 23, 2023 at 15:03

1 Answer 1


If you do the experiment with a sufficiently bright, visible light source, then the "screen" could just be a sheet of white paper that you look at with your eyes to see the projection of the interference pattern.

The screen could instead be a sheet of photographic film that you expose in the apparatus, and then develop afterward to reveal the pattern. The screen could be a CCD image sensor. It could even be a single photo diode that is mechanically scanned through the stationary interference pattern. The screen could be literally any technology that you would use to map the intensity of the light that is projected through the slits.

I do not know what they use to detect electrons or other particles for which the double-slit experiment has been performed, but the principle is the same. It's anything that can map out how many particles "arrive" at different locations in space.


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