March 15, 2021 updated April 6, 2021
See also
https://allmynoodles.com/double-slit-experiment-in-flatland-book/
https://allmynoodles.com/what-about-quantization/
We have a lamp that shines an electron/photon through 1 to infinity slits and then there’s a screen on the back to detect them. But electrons and photons are so divisible (see quantization link and below) that they travel like many small particles in a wave. They get picked up on the screen when there’s an accumulation of enough to equal to that particle.
So if we have one slit, we get a pattern like a wave one particle at a time because the wave gradually breaks the barrier of enough particles in a spot to register on the screen. Think of it like the photoelectric effect.
OK, so what if we have two slits? Then it’s like two waves and they gradually register that way. No problem so far.
Let’s say we observe a slit. Say you need 1000 “pieces” (the pieces may be differently sized but let’s just say they are the same) to equal a particle. Then it takes 1000 pieces at the same spot to register on the screen. But if you detect 1000 pieces at the same time in a slit you have detected a particle. The particle then is stuck together with time and gravity and will register like it passed through one slit and was one wave only from that slit, and you can observe both slits too.
Now what about 3 slits? 3 slits acts like 2 slits at a time.
https://www.newscientist.com/article/dn19215-triple-slit-experiment-confirms-reality-is-quantum/
Why?
When it is enough to register on the screen, it is easier to have been the result of enough to pass through 2 slits than 3, although probabilistically there’s a chance it could still theoretically be more like 3. The number passing through will keep the speed up and we will get the pattern from 2 slits. Sooner or later though, it fizzles out.
Then the same thing happens for another random selection of 2 slits, and we get the desired result.
The same is true for n slits where n>3.
Photons have no mass; so I fit them with being relays between different material objects. If they relay faster, they spread out like a star lighting everywhere. If they relay slower, they die out. So you can essentially have more than 1 or less than 1 photon in these experiments.