What is the difference between normal modes and propagation modes?

[moostang]

What is the difference between normal modes and propagation modes?

I am confused. I know that normal modes are natural modes of vibration of a system. And, propagating modes are ... ?

Thanks.

 

[Naty1]

A normal mode is a resonant frequency:
http://en.wikipedia.org/wiki/Normal_mode

A propagated wave is one imposed on a system..a forced oscillation as
in radio transmission:
http://en.wikipedia.org/wiki/Propagation_mode

I don't think these are rigidly exclusionary terms...seems to me like there
could well be overlap...like in antenna reception...

 

[Claude Bile]

It depends on the context.

In optics, propagating modes are those that accommodate propagating waves; waves that do not diminish in amplitude as they propagate (the antithesis of evanescent waves).

Claude.