Electromagnetic waves in a cavity resonator

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Discussion Overview

The discussion revolves around the behavior of electromagnetic (EM) waves in a resonant cavity, particularly focusing on how incoming waves interact with the cavity's resonant frequency and the implications for energy amplification and storage. The scope includes theoretical considerations and conceptual clarifications related to wave behavior in resonant systems.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions whether incoming EM waves at the resonant frequency will amplify the existing waves in the cavity.
  • Another participant suggests that if subsequent pulses are in phase with the returning waves, they can compensate for propagation losses and potentially use sub-harmonics for frequency doubling or tripling.
  • A different viewpoint indicates that the amplitude inside the resonator increases with each wave until it reaches equilibrium with the external amplitude, while still allowing for energy flow to compensate for losses.
  • Another participant compares the cavity to a bell, stating that tapping in phase with the oscillation can sustain the amplitude, implying a need for synchronized input to maintain resonance.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms of energy amplification and storage in the cavity, with no consensus reached on the specifics of how incoming waves interact with the resonator.

Contextual Notes

Participants have not fully explored the assumptions regarding the phase relationship of the waves and the specific conditions under which amplification occurs. The discussion also does not clarify the mathematical modeling of energy losses or the precise definitions of resonant behavior in this context.

hobbs125
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If EM waves are pumped into a resonant cavity at it's resonant frequency will each incoming wave add it's energy to amplify the wave(s) in the cavity?

I know that if you pulse a light source into a circular wave guide and you pulse the light source each time the light wave returns to it's starting point the waves amplitude will increase with each pulse inputted...

Is the same true for resonant cavities?
 
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If the initial pulse is followed by subsequent pulses that are in phase with the returned pulses you will make up for the propagation losses in the cavity. You can also use a sub-harmonic of the resonant frequency of the cavity to keep the amplitude strong and use the cavity as a frequency doubler or tripler.
 
Each wave applied will increase the amplitude inside the resonator, which acts as a store. When the amplitude inside grows until it equals that outside, we have near equilibrium, but a small flow of energy will take place into the resonator to make up for energy losses. When you stop applying waves from outside, the resonator will gradually supply its stored energy to the outside world in the same way.
 
The cavity or any other tank circuit acts like a bell. One tap and it rings and the amplitude decays to nothing. If you tap in phase with the oscillation it will be sustained. Is that what you mean?
 
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