From: Jhumki Basu (sjbasu@hotmail.com)
Date: Tue Jan 23 2001 - 20:00:24 PST
From: "Jhumki Basu" <sjbasu@hotmail.com> Subject: Graphing longitudinal waves Date: Tue, 23 Jan 2001 20:00:24 Message-ID: <F185G3ASeOxV2RQHtQl0000123a@hotmail.com>
I understand that there are two ways to graph transverse waves -- either the
graph can show the displacment of one point as time goes by, or the graph
can show the displacement of many points in the medium at one instant. But
it is unclear to me what units are on the x- and y-axis of a graph a
longitudinal wave that ends up looking sinusoidal. Specifically:
1) What exactly is being displaced if I graph the displacement of one point
in a medium through which a longitudinal waves passes?
2) What is being displaced if I graph multiple points at one time?
3) If I graph density on the y-axis and time on the x-axis, will this graph
look identical to a displacement-time graph? Why?
4) Can you explain the following statement from "Guide to Introductory
Physics Teaching" by Arnold Arons?
"Although the particle velocity is zero at the point of maximum deflection
in the transverse pulse, the particle velocity is at a maximum at the point
of maximum compression in a longitudinal pulse."
I understand the part about transverse waves, but it seems to me that a
point at maximum compression in a longitudinal pulse has a particle velocity
of zero.
5) Can one show wavelength and period on the same graph? It seems to me that
wavelength requires position on the x-axis and period requires time. But
Hewitt shows both these quantities on the same graph in his chapter
introducing waves.
6) How do you teach students to show wave motion in a graphical form? Is
there an activity you recommend?
Thanks,
Jhumki Basu
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