I Why is there no single slit interference when one slit is closed in a double slit experiment?

[PeroK]

edit: what I apparently fail to convey is this simple idea: whatever the reason, in a double slit experiment, we see something which is very similar to what we see when we use a single slit the same way. When we close one of the two slits, the second slit does not show what the first single slit did. I find it strange, and wonder how that comes. I am interested in any explanation that makes sense within the view presented. I do not have to agree with the view, but if the explanation is consistent with it, then I am satisfied.

As others have pointed out, that is classical wave behaviour. Single slit diffraction and double-slit interference. There is no mystery there.

QM only enters the picture because those phenomena are also observed using electrons, which were thought to be classical particles.

QM is also needed to explain those phenomena for very low intensity light (down to one photon at a time), where the classical wave explanation breaks down somewhat.

 

[PeroK]

PS note that your belief that single slit diffraction doesn't occur if there are two slits and one is closed is a delusion. Which could be dispelled if you had the capability to carry out the experiment yourself.

 

[Nugatory]

What interests me is what happens when one slit is closed. I do not understand why we then do not see a more or less similar pattern of interference, as we see with the single slit.

If I am understanding you properly, you are asking “Why does two slits with one closed not produce the same pattern as one slit?”
If that is the question, it was answered by BvU in #2 of this thread: Two slits with one closed produces the same pattern as one slit so there is nothing to explain.

 

[elou]

PS note that your belief that single slit diffraction doesn't occur if there are two slits and one is closed is a delusion. Which could be dispelled if you had the capability to carry out the experiment yourself.

If that is the case, then you are absolutely right. I honestly have difficulty believing the purist interpretation that is dominating this discussion. I have read many articles on the subject that are considered as "reputable" and peer-reviewed, and I have never met an interpretation like the one expressed here.
Please believe me when I say that I have no problem with this interpretation. One of the many questions that I have on the subject, is whether what we see on video clips, and is also presented in serious articles, is not a result of the different magnification level so-called interference patterns are viewed. After all, we are talking about microscopic phenomena, and each level of magnification will reveal its own details. I have asked this question one to a YouTube presenter [yes, I know!] and never got a response either.

 

[Nugatory]

I have read many articles on the subject that are considered as "reputable" and peer-reviewed

You have not, however, referenced any of these. You have referenced only misleading and oversimplified popularizations.

One of the many questions that I have on the subject, is whether what we see on video clips, and is also presented in serious articles, is not a result of the different magnification level so-called interference patterns are viewed. After all, we are talking about microscopic phenomena, and each level of magnification will reveal its own details.

Please take a moment to review the forum rules about personal speculations.

I have asked this question one to a YouTube presenter [yes, I know!] and never got a response either.

You can spend years asking questions of YouTube presenters, studying pop-sci videos and online sources, and when you're done you won't know or understand quantum mechanics any better than when you started. There really is no substitute for a decent undergraduate textbook.

The question you asked in the initial post and your followup questions have been answered so this thread is closed.

 

[PeterDonis]

What interests me is what happens when one slit is closed. I do not understand why we then do not see a more or less similar pattern of interference, as we see with the single slit.

Just to clarify: multiple people in this thread told you that, in the single slit case, we do see a diffraction pattern (what you are calling a "single slit interference pattern", although that is a bad term for it). The pop science sources you are using are simply glossing over that fact. Better sources, such as textbooks and peer-reviewed papers, will not.