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Faraday's original "Ice pail" experiments worked just fine with practically DC frequencies.
The main snag I can see with this idea is that microwave ovens are jolly good at blocking, would you believe, microwaves. Unfortunately, EMPs mainly consist of monsterwaves.
Why do EMPs damage all electrical equipment but do not interfere with human's electrical systems eg. nerve impulses.
TMS uses electromagnetic induction to generate an electric current across the scalp and skull without physical contact. A plastic-enclosed coil of wire is held next to the skull and when activated, produces a magnetic field oriented orthogonally to the plane of the coil. The magnetic field passes unimpeded through the skin and skull, inducing an oppositely directed current in the brain that activates nearby nerve cells in much the same way as currents applied directly to the cortical surface.
Back to the Faraday cage question, it's not immediately obvious that it should shield against an EM wave, but assuming it's an enclosed shell of finite thickness rather than a mesh, I think it's ability to shield is related to it's skin depth. This is essentially the depth to which an EM field can penetrate a conductor. I suspect if it were a perfect conductor, for example a superconductor, then the skin depth would go to zero and you'd have a perfect shield. Obviously the human body isn't a great conductor under most circumstances, so I'm not sure the Faraday cage argument holds up for humans.
The monster wave made me think a bit. Usually when we think of waves, they don't appreciably interact with objects that are smaller than their wavelength. Based on that, I'd expect "monster" EM wave to pass right by my MP3 player, for example, without damaging it too much. Or is wave theory misleading me here? Does the monster wave pass on by without being disturbed while still being able to destroy the mp3 player simply because the mp3 player is so small that the induced currents don't do much?
I can help you with that one (a little bit). Two parallel wires carrying parallel currents will experience a force towards each other. They wouldn't need to couple with the earth's magnetic field. As to whether it's enough to buckle railroad tracks--I don't know that one.