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Can electromagnetic fields be used as shielding for electromagnetic radiation?

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  • $\begingroup$ Could you explain a bit more what you mean by "shield"? For example, would you include radar jamming? $\endgroup$ – Rob Jeffries Aug 13 '14 at 16:07
  • $\begingroup$ @RobJeffries Shielding radiation typically means attenuating. I'm not familiar with radar jamming, but it sounds like something more related to the technology of radar (obfuscating or otherwise 'tricking'). $\endgroup$ – Paul Aug 15 '14 at 1:48
  • $\begingroup$ I am no expert, but one technique is to emit EM radiation that destructively interferes with incoming radar - that would sem to fit your definition. $\endgroup$ – Rob Jeffries Aug 15 '14 at 4:59
  • $\begingroup$ @RobJeffries Interfere is the key word here, as it indicates it is not attenuating. It seems like there would have be some effect being used that causes photons to directly interact with other photons, and I'm not aware of such an effect. All of the examples of radar jamming in the Wikipedia article do not attenuate. $\endgroup$ – Paul Aug 15 '14 at 18:42
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The short answer is no. Shielding means total absorption and light, light is an electromagnetic wave, passes mostly through light without interacting at all. All frequencies of electromagnetic radiation have similar non interacting behavior.

Matter shields are a different proposition because depending on the energy of the electromagnetic wave different materials are needed. Metal shields from a lot of the radiation , a Faraday cage for low energy radiation. At light frequencies most materials block it. At x-ray and gamma ray a lot of material is necessary for the radiation to interact and become harmless.

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  • $\begingroup$ So there can be no interaction between a magnetic field and an electromagnetic wave? $\endgroup$ – Paul Mar 22 '14 at 19:48
  • $\begingroup$ When going into the framework of the photons ( elementary particles) which build up the electromagnetic wave there are interactions with static electric or static magnetic fields , very weak, not enough to construct a shield in any sense. $\endgroup$ – anna v Mar 22 '14 at 19:52
  • $\begingroup$ Photons do not interact directly. There can be indirect interaction as photons interact with a charged particle field (like electrons) and the resulting electrons interact with other photons. This only happens at ridiculously high intensity of photons. $\endgroup$ – DanielSank Aug 31 '14 at 0:34
  • $\begingroup$ to qualify my previous comment, a the photon level the interaction with a magnetic or electric field goes with higher loops in Feynman diagrams, which involve the coupling constant 1/137 at least to the power of -16 multiplying the interaction crossection, thus the interaction with the magnetic field will be very very weak $\endgroup$ – anna v Nov 12 '14 at 6:37
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Shielding electromagnetic radiation by electromagnetic field means achieving nonlinear interaction of electromagnetic field. This can be achieved in matter (say, using gas discharge in electromagnetic fields), but requires very high fields in vacuum (http://en.wikipedia.org/wiki/Schwinger_limit ). Fields that can be created using the most powerful lasers are currently a few orders of magnitude too weak.

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