Re: Wave phase reversal on reflection

[Herbert H Gottlieb <herbgottlieb@JUNO.COM>]

On Mon, 24 Apr 2000 09:43:09 -0600 SSHS KPHOX <kphox@MAIL.CCSD.K12.CO.US>
writes:
> My colleague asked if there were a good explanatiion for the phase
> reversal when a wave reflects from a boundary where the new speed
> will be less and not when going from slow to fast. I don't have one for
her.
> Can anyone help?
>
> Ken Fox  AP/IB Physics Teacher  Smoky Hill High School, CO

This is something that I really do not understand, but I accept
it after seeing the behavior of pulses on a slinky and other
wave machines.

I always guessed that pulses, upon reaching
a boundary between a slow velocity medium and a faster
velocity medium have their energy carried away into the new
medium without difficulty.

When the pulses from a fast moving medium reach the boundary
of a slower medium, they tend stagnate at the boundary because
they cannot be carried away fast enough. This stagnation must be
almost instantaneous because the reflected pulses back into
the faster medium occur without apparent delay.

If the above reasoning sounds kinda reasonable, then could
someone explain why and how a proportion of pulses
reaching the boundary are transmitted while the rest
of them are reflected at the same time.

Herbgottlieb from New York City
(where it is easy to observe changes in pulse and wave
velocity but much harder for us  to explain why it happens)