Re: relationship between wave propagation speed and medium

Hi!

I have a question about the relationship between wave propagation speed and medium.

We know the fomula of wave propagation speed is Vp=1/√ε.

It seems that wave propagation speed is decided by the mudium. But we also know wave length is decided by its frequency. A signal with higher frequency has a shorter wave length. Does the wave propagation speed has no relationship with frequency?

Added after 25 minutes:

My question is the wave propagation speed or propagation delay of two signals with different frequency will be the same when they pass through the same medium?

Hello,

The propagation speed in a uniform medium is:

v_prop = 1/(Re{sqrt(perm*eps)})

Re = real part of, perm = magnetic permeability, eps = permittivity.
Do not use relative values. When, for your range of frequencies, these material constants do not vary, the propagation speed will not vary also.

I hope this helps you forward.

Theoretically it sounds same.
what if the medium has the limitations with freq?
signal will die soon than propagation.

Hello,

You are right, in many media (like metals), the attenuation is that high that the wave died before it had time to propagate one wavelength.

for the skin depth (attenuation to "e" [ 2.71828]), you can use:

skin depth = -1/(2πf*Im{√(μ*ε)} = 1/α

For materials with significant conductivity, you have to convert the conductivity to an imaginary epsilon. Epsilon has a real part (that accounts for the capacitive effect), mostly denoted with e' and an imaginary part (that accounts for the loss), mostly denoted with e'', where you have to add "-j" in front of it.

I don't know what type of media the original poster had in mind, but now he can evaluate the complete propagation constant for his media.