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Re: A physics project



Hi,
If you are trying what I think you are it is called
sonoluminescence. If so look at the following article.

One source is the Scientific American article:
Light, Producing from a bubble of air,
Robert A. Hillier and Bradley P. Barber
1995 Feb, pg 96

It is a good semester long experiment for good, highly motivated
students, but it not an easy experiment. Here at the University of Arizona, we have twice had
very good undergrads do sonoluminescence, and both time the students
worked a long time before seeing anything. Degassing the water
and then introducing the right amount of argon is just one problem.
The tuning of the frequency and the amplitude to get a stable bubble
is at best laborious. Also the bubble is not very bright, and
I think one of the students probably was producing the effect for several
week before he really did a full black-out of the room, and saw the glowing
bubble.

The items you need are a spherical flask, several ultrasonic
transducers ( see Sci Am article for sources) stable frequency generator,
good audio amp, probably a transformer, variable capacitor, and a variable
inducter to get a good impedance match between the inductor and the amp.
A fair o'scope is needed for tuning. ( The problem with scopes is the the
bubble glows greenish and the refrection of the scope's screen on the
flask is also greenish.)

Thanks
Roger Haar


*************************************
I would be very interested in finding out more about generating
light from sound. Sounds (pardon the pun) like an excellent project
for students.

Please send me the information
Oren Quist, SDSU
quisto@mg.sdstate.edu
or
Physics Department, Box 2219
South Dakota State University
Brookings, SD 57007

Thanks.