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When an electron absorbs a photon, there it accelerates and thus it creates a kink in its electric field. Then, when it falls down to its normal state, it creates another kink. Here are my questions.

  1. Is an electromagnetic wave the "going up" AND "coming down" of the electron? In other words, is an EM wave both of the kinks?

  2. If not, and it is just the kink created when it falls down, doesn't that mean the electron "sends off" another EM wave, because only one kink creates an EM wave?

Thanks in advance.

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To use a somewhat quantum fieldy but handwavy description (as would probably be enough in this context), the electron in the ground state behaves like an "antenna" for EM radiation of the correct wavelength. The resonance between the electron and the EM field allows it to absorb the photon and change its own wavefunction to the more energetic one ("go up").

When it releases the photon ("goes down"), the same thing happens in reverse (you end up with an additional EM excitation and a change in the electrons wavefunction state).

I'm not sure how to clearly answer your 1 and 2 questions as the preamble is a bit confusing.

Whats missing from this description (among many things :) is why/when it happens. All kinds of interesting stuff lives here like lasers (existing EM waves help an electron to release its energy into the same wave state as the existing wave).

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  • $\begingroup$ Sorry for the confusing preamble. This answered my question nicely! However, I do have a question: are electromagnetic waves caused ONLY by accelerating charges, or can they be created through other atomic methods? $\endgroup$
    – Queso Pez
    Commented Oct 1, 2019 at 15:18
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    $\begingroup$ @QuesoPez Sorry for the late reply.. it's a bit difficult to answer such questions as it's a classical description while it's not "really" working like that. Photons, the EM carriers, are emitted and absorbed by charged particles all the time, but only some particle configurations over time generate photons that can propagate to a more distant place (an "EM wave"). In the schoolbook examples this is given for example when an electron is linearly accelerated, but it stops being a useful analogy further on I think (like in your original example with the electron transitions in an atom). $\endgroup$
    – BjornW
    Commented Oct 7, 2019 at 11:59
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    $\begingroup$ @QuesoPez Everything is further complicate by the fact that a "photon" sometimes means a distant propagating wave-like photon (sort of a "semi-classical photon"), sometimes it means any perturbation in the EM field (often called a "virtual photon"). What we are talking about when we say "EM waves" is mostly then a photon with proper wave-like characters with a reasonably well-defined wavelength and reasonably spatiotemporally defined origin and destinations. $\endgroup$
    – BjornW
    Commented Oct 7, 2019 at 12:02

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