Re: Waves

[Bob Sciamanda <trebor@VELOCITY.NET>]

> . . .
> Bob's point that purely vertical motion of a string wave is over-simplified
> is definitely related to my question. Again, please elaborate and I'll go
> look up the AJP article next time I'm at the library. Carl
>
> Dr. Carl E. Mungan, Assistant Professor     http://www.uwf.edu/~cmungan/
> Dept. of Physics, University of West Florida, Pensacola, FL   32514-5751
> office: 850-474-2645 (secretary -2267, FAX -3323) email: cmungan@uwf.edu\


This sadly neglected paper is MUST reading.

By constructing a more realistic model, this paper develops a picture of a
string wave which departs significantly from our usual view of simple
harmonic motion of each particle.  Besides answering the problems raised in
this thread, quite different conclusions are reached on other matters:  eg.;
"At any point x on the string [supporting a traveling wave] the potential
and kinetic energies of a length dx are always equal in magnitude and in
phase."  Elsewhere: "In the case of standing waves, the energy surges from
the nodes, where it is entirely potential, to the antinodes, where it is
entirely kinetic, and back again."  There's lots more, including similar
conclusions about longitudinal mechanical waves.

A follow-up note - Mathur & Sastry, AJP 51 (3), 276-277, March 1983 -
confirms the above and draws analogous parallels in E&M waves.  Don't wait -
read them both now.

Bob

Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor