Waveguides and Cavity resonator Equation confusion

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Discussion Overview

The discussion revolves around the differences in wave equations for rectangular waveguides and cavity resonators, focusing on the mathematical representation of wave propagation and standing waves in these structures. Participants explore the underlying principles and equations without reaching a definitive conclusion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant expresses confusion regarding the different forms of the wave equations used in rectangular waveguides and cavity resonators, specifically the use of d²/dz² = Gamma² for waveguides versus d²/dz² = -Kz² for cavities.
  • Another participant suggests that the difference arises from the nature of wave propagation in waveguides (propagating waves) compared to standing waves in cavities.
  • A later reply indicates that the standing wave condition in a cavity necessitates specific boundary conditions, which can be derived through separation of variables in the wave equation.

Areas of Agreement / Disagreement

Participants generally agree on the distinction between the wave equations for waveguides and cavities, but the discussion does not resolve the underlying confusion regarding the mathematical treatment of these concepts.

Contextual Notes

Participants mention boundary conditions relevant to cavity resonators, indicating that the equations depend on specific assumptions about wave behavior in different contexts. The discussion does not clarify all mathematical steps involved in deriving the equations.

Dhruv
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Homework Statement


This is not a homework question and I am asking this question out of curiosity. We have been taught rectangular wave guides and cavity resonator recently and I don't want to gulp the wave equations as it is, so the problem that I am facing ( I have written it on paper and uploaded the photo) . Don't know if my question is stupid but it really confuses me .

Homework Equations

The Attempt at a Solution

 

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Hello
I don't know exactly what is your problem but I assume you confuse why in rectangular wave guide we set d^2/dz^2=Gama^2 but in cavity d^2/dz^2=-Kz^2?
As you know in the wave guide we transfer a wave in Z direction and it goes through wave guide with it's wave coefficient (Beta) but in cavity a wave repeat simultaneously in the cavity in +Z and -Z direction to create a fix resonator so it should be in sinusoidal form
 
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baby_1 said:
Hello
I don't know exactly what is your problem but I assume you confuse why in rectangular wave guide we set d^2/dz^2=Gama^2 but in cavity d^2/dz^2=-Kz^2?

Yes this is what I am confused about. Thank you for reply :) , it helped a lot . So this means I am making changes in equation because I know that in resonator my wave has to be a standing wave rather being a propagating one in +z or -z direction.
 
Hello
Yes of course ,However you can try to solve wave equation in cavity and use separation variables to obtain it's answers after that you should add two new boundary condition ( E tangential in EZ(0)=EZ(d)=0 )that only a sinusoidal form can prove that.
 
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Thank you :)
 

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