This question How can photons destructively interfere?, definitely and clearly a question about photons, was made duplicate to a general waves question: What happens to the energy when waves perfectly cancel each other?.

Photons are not waves. They are quantum mechanical elementary particles and their wave nature appears in the wave function, leading to probability amplitudes, not energy in motion in three-dimensional space.

There is no evident way to vote for unmaking the duplicate action.

Edit after answers:

I realize there is a way to reopen, but it is not obvious on the panel of duplicate. How can I vote? By having it hidden, a lot of people who would agree with me do not have a chance to vote. I am on this site practically for ten years (that is why I have a high reputation; years count). Still I do not know how to put a duplicate on a reopen course, and I am sure there are many others like me.

I propose to put a link on the duplicate panel that leads to the decision queue.

Again, I think it is a bad decision: "Yes, the mathematics of wave equations is the same for classical energy waves and for quantum mechanical probability waves the physics, i.e. data, is not. Probability and energy are two different concepts defined axiomatically in physics theories and to send a new student of physics to dig out from the mathematics the relevant answer is at least not consistent with the aims of the site.

Edit 2 Question was answered in a comment by MassimoOrtolano:

The usual line, below the question for flagging or requesting closure, is

share cite edit follow close flag

is variable and becomes

share cite edit follow reopen flag

which I had not noticed up to now.

  • $\begingroup$ Isn't "reopen" active on that question (I couldn't see it - I have less than 3,000 reputation points)? $\endgroup$ – Peter Mortensen Dec 18 '20 at 21:03
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    $\begingroup$ The reopen review on this question has concluded 3:1 in favor of "Leave Closed". $\endgroup$ – ACuriousMind Mod Dec 18 '20 at 21:06

What to do when a question is made duplicate to a not really relevant other question?

You vote to reopen. If others agree, they will vote too and it will be reopened. If not, then it will stay closed.

FWIW I voted to reopen.

  • $\begingroup$ I do not know where one finds to vote to reopen. I think that it should be clearly shown in the table showing the duplicate. there is no link $\endgroup$ – anna v Dec 19 '20 at 5:49
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    $\begingroup$ @annav The reopen button is at the bottom of the question, right below the tags: the buttons for a closed question are, in order, share, cite, edit, follow, reopen and flag. $\endgroup$ – Massimo Ortolano Dec 19 '20 at 10:00
  • $\begingroup$ @MassimoOrtolano Thank you. I did not know that that location is variable . $\endgroup$ – anna v Dec 19 '20 at 10:05

That question does mention photons as quanta of energy, but the meat of the question is purely classical—asking about things like destructive interference and the phase, which do not apply to photons (at least, not in the way the question assumes). So the physics of any meaningful answer is going to be essentially classical field theory.

I thought about whether the question was a duplicate, but I ultimately decided not to flag it and to answer it instead. However, there is certainly an colorable argument to be made that the duplicate does provide all the necessary information about what is going on. It is an edge case, and once it had been closed by a gold badge user, I voted not to reopen it when it came up in the queue.

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    $\begingroup$ Wrong decision .Probability waves and energy waves are two different models used in physics and should be always made clear, not buried udner a lot of mathematics. $\endgroup$ – anna v Dec 19 '20 at 5:54

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