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

[Bernard Cleyet <bernardcleyet@redshift.com>]

My last experiment was a slight disaster.  I used the black insulation 
on the low potential wire to the cells charger for the camera supply.  
Some of the plastic melted onto the plastic diffusion lens of the 
flash.  I can't use solvent,  as the plastics are too similar.  I'll try 
scraping..


A typical lamp supply is 300 V. w/ a 13 => 40 microF cap.  For the small 
cameras I'll calc. using 20 microF.  That's  about one Joule.  Assuming 
a Xe lamp it's main peak is at ~ 0.9 microm, a secondary at 0.85, and 
the third broad at 0.45.  This is for an ~ 0.2 J capillary lamp, seven 
cm X 0.5 mm d.  p.=0.8 atm.  Output is always above 50 E-6 J/sterrad. mm 
micron.

Integrating by eye, I estimate 44 milliJ or 22% efficiency.  The 
efficacy is about 40% of that (8%).

So the heating E is ~ 44 milli J.  in ~ 100 E-6 s.   Since it
is dumped in a short time only the surface is heated, which IMAO is the 
reason for the acoustical effect.

bc, waiting for critique.



Brian Whatcott wrote:

> 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!  
>
>
> _______________________________________________
> Forum for Physics Educators
> Phys-l@carnot.physics.buffalo.edu
> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
>
>
>