Jeff Liebermann wrote in
:

Without a
reflection, there can be no standing waves.


That's the one bit that comes naturally to my own understanding, such as it
is. How far does this parallel with an optical laser cavity? I'd find it
easier to understand if someone here who knows both can point out a few
essential similarotes and differences.

Also, in the ringing of a resonant audio filter (or any electronic filter),
there seem to be parallels there too. After all you can only have ringing, a
note produced, while energy remains in the system.