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I am actually no physicist , but a computer scientist. Probably you will want to personally murder me for asking such a dumb question , but I have no knowledge of physics and I am asking out of curiosity.

As far as I understand , photons die out when they interact with other matter. Thus , when a photon interacts with an electron of a lower energy level , the latter absorbs the photon and charges up and after a while discharges (emits the energy difference). And my question is :

Can a magnetic (or other field) stop light in mid air ? For example , assume that a flashlight it pointed towards a wall , and there is a field in between the two latter objects. Is there a way that such a field may stop the light before it ever interacts with the wall ? In other words, imagine that you are witnessing the light being projected from the flashlight and then just disappearing mid distance and never reaching the wall. And again , please understand that I am a complete newbie in physics and I am asking just out of pure interest.

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  • $\begingroup$ Hi, welcome to Physics SE! You don't have to apologize for asking a question, though it might have prevented your question from being too harshly downvoted. :) $\endgroup$
    – stafusa
    Commented Aug 11, 2017 at 21:42

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No. There's nothing non-material (my interpretation of what was meant here with "field") one can use to stop the flashlight beam before it reaches the wall.

In everyday scales, light (essentially) doesn't interact with light in plain air, and there's no field of only electric charge it could interact with. In high energy physics photons can interact (see Two Photon Physics) and strong enough gravity might deviate the light before it reaches the wall, but I don't think such situations fit the everyday gist of the question.

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  • $\begingroup$ Would you consider W bosons "non-material", but a field? Since they are charged, they could conceptually stop photons. Although indeed not in everyday life. $\endgroup$
    – safesphere
    Commented Aug 15, 2017 at 17:34
  • $\begingroup$ They're not ordinary matter, but rather force carriers [ en.wikipedia.org/wiki/Matter#Based_on_quarks_and_leptons ]. Of course, in QFT everything is a field, including "matter", e.g., electrons, but that doesn't seem to be what the OP had in mind with the word "field". $\endgroup$
    – stafusa
    Commented Aug 15, 2017 at 20:37
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As far as just the magnetic field itself, no. Since the EM field is almost like the "medium" that light travels through, it'd be like putting extra water in between a boat and shore to try and stop the wake from hitting shore.

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Thus , when a photon interacts with an electron of a lower energy level , the latter absorbs the photon and charges up and after a while discharges (emits the energy difference).

No. Please forget about the electron acquiring charge from the photon, an electron has always has the same electric charge, that never changes under any circumstances.

A photon does not carry a charge itself, it transfers momentum. If photons did carry electromagnetic charge, there would be a spreading of light as soon as you turned a torch on, due to mutual repulsion.

The magnetic field will not affect the photon, but it will affect the charged electron, as in the aurora at the poles.

What the photon does is add momentumm to electron, not charge, to allow it to change energy levels or even completely leave the atom , (ionization).

This might take a few reads, but it will explaIn your question in greater detail: Photon Electron Interaction

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    $\begingroup$ Pretty sure "charges up" means "gains energy", not describing a change in charge. $\endgroup$
    – Zhengqun Koo
    Commented Aug 12, 2017 at 5:05
  • $\begingroup$ @KooZhengqun That could be true. It is just that "dies out" earlier to me implied, the (mistaken) idea that a photon carries a charge, gives it to the electron and then disappears. Regards $\endgroup$
    – user163104
    Commented Aug 12, 2017 at 7:48

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