# How does the double slit experiment prove super position?

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I know this question has been asked before but I have only found threads for it at an undergraduate's level of understanding and I am just finishing ninth grade. How does the double slit experiment prove superposition? What led me to ask this question, was that, since when you close one slit the pattern you would otherwise see if both slits were open disappears, it must mean that the electrons are going through both slits simultaneously(In a ted talk about Schrodinger's cat). But, the diagram showed that electrons were being sent individually through each slit. Couldn't this mean that the reason the pattern isn't being seen is because the electrons are only being sent through one slit instead of two? Maybe, now that there is only one slit, it is harder to identify the wave pattern.
It just seems like a real jump to say that, pattern disappears, therefore superposition. I tried to read this paper on the double split experiment, but I can't comprehend the Math yet, so it's essentially useless.
Can you please give me an explanation that a high schooler can understand?
P.S
I am not debating whether or not the double split experiment shows an example of superposition. Based on the number of times this test has been done with the same conclusions again and again I can guess it is almost definitely correct. But I just can't seem to understand it.

I am not debating whether or not the double split experiment shows an example of superposition. Based on the number of times this test has been done with the same conclusions again and again I can guess it is almost definitely correct. But I just can't seem to understand it.
The double slit experiment, that when unobserved individual electrons form an interference pattern, but when observed which slit they pass thru there is no interference pattern, is a weird aspect of nature. Superposition is a mathematical construct (part of QM) that provides an aid in calculations and cannot be claimed to be a "part of reality" .

bhobba
bhobba
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Can you please give me an explanation that a high schooler can understand?

Sorry - that's the reason you are fed half truths at the beginning - you dont have the background to understand the full truth. It is unfortunate its like that - but that's the way it is.

https://www.amazon.com/dp/0691024170/?tag=pfamazon01-20

Thanks
Bill

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Khashishi
The double slit experiment can be explained using classical electromagnetism, without any quantum mechanics.
Superposition is a principle in electromagnetism where the electromagnetic field from two sources is just the sum of the electromagnetic field from one source. Interference occurs because in some places the electromagnetic field from each source are pointing mostly in the same direction and add together, and pointing in opposite directions in other places and subtract.

It might be worthy of noting that if you really did such experiment with electrons and compared it to the same experiment with a laser (say), then the results would NOT look exactly the same. The electron result would be speckled, the photon result would be smooth. Both would show (for two slits open simultaneously) interference, with the intensity in the light picture smoothly increasing and decreasing and in the electron detector the result would show more and less speckles (spots). So, even though the electrons are interfering 'like waves' they are still hitting the target detector 'like particles'.

Nugatory
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The electron result would be speckled, the photon result would be smooth.
A beam of light delivers an enormous number of photons to the surface it illuminates, so we're accustomed to seeing smooth patterns from light. However, if the number of particles involved is roughly the same, then the graininess of the pattern will be similar.
So, even though the electrons are interfering 'like waves' they are still hitting the target detector 'like particles'.
An individual photon also leaves only a single dot at a single point on the screen - they're no less particle-like than the electron in this respect.

Nugatory
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The KEY point about the double slit experiment, is that you get an interference pattern when you are sending ONE ELECTRON AT A TIME through the slits. A
This is a good point, one that bears repeating: the double-slit experiment best demonstrates quantum superposition when you do it with both slits open and send a single particle at a time so individual dots appear at the detector, one at a time. It is very difficult to explain the interference pattern that gradually appears under these conditions as anything except quantum superposition.

The lack of interference pattern when one slit is closed is a fascinating example of how quantum mechanics works (weird that when we're sending one particle at a time it matters how many slits are open) but is a less convincing argument for superposition. With one slit open we don't expect an interference pattern and we don't get one. However, a sensitive enough experiment will find a diffraction pattern, so the wave nature of the particles is still demonstrated even though superposition is not.

Markus Hanke and bhobba
bhobba
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The lack of interference pattern when one slit is closed is a fascinating example of how quantum mechanics works (weird that when we're sending one particle at a time it matters how many slits are open) but is a less convincing argument for superposition.

Indeed. As the paper I keep linking to explains one slit open is explained by the uncertainty principle. Two slits is the uncertainty principle plus superposition.

Thanks
Bill

(with a single slit) the wave nature of the particles is still demonstrated even though superposition is not.
Single slit diffraction happens when the slit is not very narrow. It is interference between wave fronts that have passed through different parts of the slit. So perhaps in quantum terms we can think of it as a superposition of going through many different parts of the same slit...?

bhobba
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So perhaps in quantum terms we can think of it as a superposition of going through many different parts of the same slit...?

Sure. Again as the paper I keep linking to explains a slit of non infinitesimal width is broken into a lot of slits of infinitesimal width and the superposition taken:
http://arxiv.org/ftp/quant-ph/papers/0703/0703126.pdf