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I want to know is there interaction between photon and electric or magnetic field? In other word can I deflect photons by electric or magnetic field? If it is possible, under which condition one can deflected photons direction by electric or magnetic field practically?

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  • $\begingroup$ See gamma-gamma collider theory about that. It would take extremely high fields to do that and in practice it simply doesn't happen in nature, maybe except under the most extreme circumstances, but then it would be swamped by other effects involving matter. $\endgroup$ – CuriousOne Jun 9 '15 at 18:37
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Photons don't carry an electric or magnetic charge, so shining a light near a magnet will not deflect the light beam. Neither will an electric charge affect them.

Again using the light / torch example, if photons did all carry, say a positive change, the beam of light of a laser would spread out as soon as it left the end of the instrument.

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"is there interaction between photon and electric or magnetic field" With an everyday magnet not so much. With the strongest magnet in the universe, comprised of a super dense substance such as a magnetar (which is dang near a black hole but it's a type of neutron star) You can actually split the photon into two photos!

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There is an interaction between photons and a magnetic field. A strong magnetic field will change the polarization of light - see Faraday experiments.

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    $\begingroup$ Light in a medium is not the same as the light in vacuum. There is no Faraday effect in vacuum. Medium strongly determines what is light in it. $\endgroup$ – Vladimir Kalitvianski Jun 9 '15 at 19:15
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Since electric and magnetic field really are photons the question you are asking can be rephrased as: "Are there any photon-photon interactions nature?"

From a quantum-electrodynamics (QED) perspective the answer is YES! However at tree level there are photon-photon procedures. This is mainly because photons only couple to charged particles such as electrons and quarks.

There is however higher order processes which involve virtual electrons that enable photon-photon scattering.

With that said these processes occur at photon energies comparable to the electron mass. This is far from the long wave-length limit that typically constitute macroscopic electro-magnetic fields. Thus in an experiment of the type you are suggesting measuring this effect would be difficult.

ADDED BY REQUEST IN COMMENT: I have not done any proper loop calculations myself so I do not know precisely where to start looking for the details of photon-photon scattering. For an introduction to QED you could use either Peskin & Schroeder or Mandl & Shaw. Perhaps this case is covered in one of these books.

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  • $\begingroup$ Dear Mikael. Thank you for your useful answer. My idea is to setup an experiment for deflecting gamma rays by high voltage. So 1-Could you introduce me references about photon-photon interaction, and 2-Do you have any idea about practical condition about above experiment? $\endgroup$ – Vahid Jun 10 '15 at 0:02
  • $\begingroup$ In QED its not virtual photons that cause the lowest level interaction diagram but virtual electrons (positrons), as the only allowed vertex shape is a photon to two electrons (positrons). $\endgroup$ – Triatticus Jun 10 '15 at 11:45
  • $\begingroup$ @Dan: Sorry, my bad. I meant virtual electrons. I'll change my answer accordingly. $\endgroup$ – Mikael Fremling Jun 10 '15 at 18:31
  • $\begingroup$ @Vahid: Added some references in the reply. $\endgroup$ – Mikael Fremling Jun 10 '15 at 18:46
  • $\begingroup$ No problem, i probably should have kept mine a little more general too and just left it at charged particle $\endgroup$ – Triatticus Jun 10 '15 at 18:57

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