Hello.
Let's say plasma is discharged inside the vacuum chamber which is completely shielded and properly grounded to earth. Then radiation comes out from plasma. Let's say RF frequency radiation comes out then they should be bounced many times inside the chamber as a good Faraday cage. Question is how they can decays? I don't think they're trapped for infinity time. Maybe the radiation excites surface charge which requires some energy of the radiation and that charge distribution will be balanced out due to grounding, eventually all radiation energy is spent in this way?
All energy at some point gets converted into heat, so presumably this is true for any inside a Faraday Cage. Some energy would be reflected from the walls, but presumably that is not a 100% efficient process.
It is dissipated as eddy current losses (heat) in the walls of the Faraday cage. As incident EM waves approach the walls, they induce mirror currents in the walls which reflect the waves. However, since the walls have finite electrical conductivity, a small amount of energy is lost during each bounce, causing the RF energy to decay. Eventually, the original energy is dissipated as joule heating of the walls, Similar losses govern the overall Q of a cavity resonator.
Answer r absolutely correct. However I just want to add something more with an example....it is true that all the heat is dissipated in the form of heat, but as a whole instantaneously....for example inside the car....The roof can be assumed as a wall of faraday cage and the radiation inside the can can be dissipated if the car has properly mounted Antennas in the car..... Because most vehicles have metal roofs and largely come with factory tinted glass, your vehicle can act as a Faraday cage and concentrating reflector, amplifying RF wave density like a microwave oven, not letting the RF radiation escape through the metal body and tinted glass, and then concentrating the microwaves into your body at much higher EM intensities. It’s highly recommended you use antenna kit or car kit to wave guide (transport) the RF Radiation outside the vehicle to prevent amplification of the microwave effect.
If you think of a microwave oven with nothing inside then the RF energy must heat up the water vapour in the air too. Air also has a loss associated with it. Presumably that would constitute some small loss which would if as Bert says you get lots of reflections.
Oh thanks people. My mind becomes nuch more clearer than before. All things you guys mentioned just make sense.
I suppose that a transmitter antenna system properties inside a Faraday cage, do change, both in terms of radiation pattern and VSWR value. Actually the return loss increases and energy is transformed to heat inside the transmitter itself.
However since nothing is ideal (including and microwave ovens), part of the energy may leak. Thus turning on a microwave oven, without any food inside, is dangerous not only for the device, but also for people near by.
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