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As predicted by Huygens' principle it seems obvious that light can produce light. Is it true or I have a misconception?

I asked this question because what I have learnt till now is that light can only be produced by accelerated charges but Huygens' principle gives whole different concepts. It says that each point of wavefront can behave as source for new wavelets. It means light can produce light. Is it so?

Ruslan
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Shreyansh Pathak
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    That depends on what you mean by “produce”. Can you make your question more precise? – G. Smith Oct 10 '19 at 18:49
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    Certainly a particular amount of light energy does not create any additional light energy. – G. Smith Oct 10 '19 at 18:50
  • @G. Smith please see the edited version as it's easy to downvote for everyone.All the physicists at this website must be English literature experts. – Shreyansh Pathak Oct 10 '19 at 19:05
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    @Unique People on this website need to be able to understand what you are asking. It's nothing to do with being English experts. Words have specific meanings, and since we're communicating using those words, you have to use them correctly if you want other people to be able to understand the question you are actually trying to ask. In this case, the original question was just the first sentence. You didn't explain how it seems obvious that the Huygens principle produced light; you just said it was obvious and asked if it's true. To many, it is not obvious what you meant by that. – JMac Oct 10 '19 at 19:20
  • @JMac The website must make sure that everyone is fairly treated on this website.There must be no partiality.I just said it is easy to downvote.It is more easier to leave this website. – Shreyansh Pathak Oct 11 '19 at 03:24
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    @Unique I don't understand what is unfair. Downvoting unclear questions is an intended feature of the site. It even says as much when you hover over the downvote button. You shouldn't assume downvotes are personal. – JMac Oct 11 '19 at 03:37
  • Considering how annihilation and creation operators are used to describe the movement of particles on lattices ("hopping"), I wonder if in some cases one could actually describe light propagation as light being destroyed at a spot and created further ahead. – stafusa Oct 11 '19 at 07:54

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No. The most reasonable way to think about what it means to “produce” light is to consider “production” to be the transformation of some other form of energy into light energy. Thus the kinetic and electrostatic potential energy of an excited electron in an atom does produce light, but light does not produce light. Huygens' principle helps explain how light propagates, not how it is produced. When light propagates in space, its energy just moves around; no additional light energy gets created.

Ruslan
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G. Smith
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  • Well photons can turn into two photons in strong magnetic field. https://physics.stackexchange.com/questions/13851/can-you-split-a-photon – MiltonTheMeme May 22 '20 at 12:25
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No. Fundamentally, for light to be able to produce light, photons should couple to photons. In QED, there is no such interaction. In other words, a photon is not electrically charged. So, there is no Feynman vertex where a photon can decay into two or more photons. So, there is no process in which light can produce more light by itself.

That said, there are loop diagrams where, effectively, it would look like $n_1$ photons scatter into $n_2$ photons where $n_1$ may or may not be the same as $n_2$. (See this famous box diagram where two photons scatter into two photons in a one-loop process.) If one wishes, one can say that in this scenario, effectively, the light produced more light. (Of course, the momentum and energy would be conserved!) However, notice that fundamentally, light didn't produce more light "by itself". The loop processes involve the decay of a photon into an electron-positron pair and there still isn't any direct interaction between a photon and a photon.