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Re: [Phys-l] Strobe makes aluminum can go "ting"



At 07:09 PM 4/21/2007, Tony Wayne, you wrote:
...
Take an empty aluminum drink can and place a camera's strobe in front of the
can. Face the light from the strobe at the can. Place the strobe about 1/2 a
cm in front of the can. Charge and then trigger the camera strobe. When the
flash occurs, you will hear a, "ting," sound from the can. The question is
what is causing the sound?

If I move the strobe about 3 cm away from the can and triggered, no sound is
heard from the can.

If I aim the strobe perpendicular from the can and trigger it, no sound is
heard from the can.

If I place the strobe about 1/2 cm in front of the can can place one sheet
of notebook paper between the strobe and can the sound is diminished.

If I place the strobe about 1/2 cm in front of the can can place six sheets
of notebook paper between the strobe and can, no sound is heard.

If I place the strobe about 1/2 cm in front of the can can place a piece of
manila folder between the strobe and can, no sound is heard.

If I try the flash from my digital camera I don't get any sound under the
original working conditions. However my friend's digital camera works and
well as my older (removable) camera strobe.

At first we thought it was an and emp from the capacitor in the strobe's
firing circuit. (But, I don't have a faraday cage handy to test this at the
moment.) But now that I've done the experiments, above, I'm not so sure it
is an emp.

Any ideas or thoughts?

-Tony
--
Tony Wayne
Albemarle High School
physixdude@comcast.net
http://www.mrwaynesclass.com


It's true that my first association was to the wing
leading edge deicer an engineer at a NASA lab created
some years ago.
A capacitor discharge current pulse led down two adjacent
conductors along a wing created a high-g jerk that atomized
ice adhesions.
Here's the latest commercial development of that approach.
<http://www.idiny.com/eidi.html>


However, the contrary evidence is that light shielding stops the sound.
So this compares more to pulsed opto-acoustic spectrometry.
[aka photo-acoustic spectrometry). A light pulse at a suitable
frequency provides an acoustic pulse due to molecular absorption.

I tried to find a URL with a bare bones example, but the candidates
were all a little high-flown. Here's one that's somewhat accessible.

<http://rpd.oxfordjournals.org/cgi/content/abstract/17/1-4/259>


Brian Whatcott Altus OK Eureka!