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The single photon / single electron double slit experiment shows particles appearing as dots on the screen. This is explained as being due to the collapse of their wavefunctions.

However, if they were point particles, we would not be able to see them at all. Instead, they have a radius upto which they appear as bright. That would mean there is some intensity of light emitted by the screen after absorption of the photon.

The light will not have the same intensity throughout that radius, and would decline along the radius. How can we quantitatively measure either the intensity of the incoming radiation along the surface of the screen or the intensity of light emitted by the screen?

Blacklight MG
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  • CCD imagers are pretty quantitative. And why should the screen have an electric field? – Jon Custer Feb 06 '24 at 13:06
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    Why the close votes? This is a perfectly clear question. – John Doty Feb 06 '24 at 13:34
  • The ear for sound! – Farcher Feb 06 '24 at 13:43
  • @JonCuster CCD was exactly what I was asking about. They are measuring the charge density created by the fields.. so I wanted to know that. – Blacklight MG Feb 07 '24 at 09:16
  • Interference of what: electrons, light, x-rays, microwaves, water waves, …? You mention a "screen", so it is unlikely to be water, but electrons, light, and x-rays could also by imaged by a screen. (And that does not include interference observed on an oscilloscope screen.) What is the wavelength? What is the size scale of the interference pattern? What is the intensity? Why do you want to quantitatively measure the pattern? I did not notice this question when it was posted or vote to close it, but I understand why it was closed. – David Bailey Feb 14 '24 at 15:17
  • @DavidBailey I was talking about generic electromagnetic wave interference, but the same applies for electrons as well. But not water. Intensity should be the electric field obtained at the screen due to the light falling on it. I want to measure it to see how concentrated the the intensities are at different oarts of the screen, aside from visual observations, which may be due to optical illusions too. – Blacklight MG Feb 15 '24 at 05:43
  • No single type of instrument can detect "generic electromagnetic waves", but only some specific region of the electromagnetic spectrum. Specifying that you want to measure the electric field actually confuses the issue. You can make "screens" of CCD or photographic film, but these are quantum devices that count photons (or electrons) with high enough energy; they do not directly measure the electric field. On the other hand, microwave detectors do measure the electric field, but microwave interference is usually measured by scanning a detector across the pattern; no screen is involved. – David Bailey Feb 15 '24 at 16:56
  • @DavidBailey I mean I wish to know the radius of the photon. I though the electric field would be the right value to measure. By generic I meant any, such as UV or IR, not all. – Blacklight MG Feb 15 '24 at 17:24
  • If you want to know how the "the radius of the photon" could be experimentally measured from an interference pattern, you could ask about that, but first look you'd need to define what you mean by "radius of a photon". I suggest looking at "Can a photon have a radius?" and "What is Size of Photon?". – David Bailey Feb 15 '24 at 18:27
  • @DavidBailey I'm referring to the radius of the photon as observed in the interference pattern, when the wavefunction collapses. If it was a point particle, we wouldn't see anything, but we do. So what exactly is happening there? – Blacklight MG Feb 15 '24 at 18:33

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For light, usually we use some sort of photoelectric detector like a CCD to sense the intensity.

For a radio version of the experiment, you can scan the field by moving an antenna and measure the amplitude with a radio frequency voltmeter.

John Doty
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  • According to this answer, apparently CCD does not measure individual photons. I was curious as to whether a photon is a dot or a continuous spread, but the intensity at the center is relatively higher than the surroundings, making it look like a point spot. – Blacklight MG Feb 07 '24 at 09:25