Understanding Electromagnetic Field Propagation: Insights and Formulas

[AgerPl]

Homework Statement

Hi this is my first post I hope that my explanation is good.

Now this is the explanation. Now I will provide the known values.

So I start looking literature and some formulas to solve this and I found two different propagation constants. Gama and Beta.

Homework Equations

or

The Attempt at a Solution

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But even if I realize which one of these formulas to use I can't really understand why the dispersion equation is given if I'm not using it. Really need some insights here.

I hope you can help me,
Many thanks to you

 

[AgerPl]

Hi,

Nobody can give me insights?BR,
Ager