Re: The sound of a laser.

From: Sam Goldwasser (sam_at_saul.cis.upenn.edu)
Date: 10/17/04 

Date: 17 Oct 2004 10:05:02 -0400

A few mJ is enough for air breakdown from a low f/ number focused Q-switched
laser. Yes, there is the sound of the caps discharging. That's not what
is being discussed here.

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"Ian" <not_at_here@hotmail.com> writes:

> i suspect the sound reported from any high energy laser is more likely to be
> the crack due to the relaxation of the dielectric in the capacitors. Itd
> have to be some energy/(not power) level to heat the air up enough to
> produce a shock wavefront. Still... if you dress it up enough and give it a
> swishy name, theres bound to be some hi-fi nut with a turntable and valve
> amp that would think it was the best tweeter he'd ever heard ie inertialess.
>
> "Helpful person" <rrllff@yahoo.com> wrote in message
> news:87946313.0408200441.785a361b@posting.google.com...
> > "David Prokopetz" <sirbob@penguinking.com> wrote in message
> news:<2ol510Fbmdq4U1@uni-berlin.de>...
> > > Hi.
> > >
> > > Physics newbie question here: what does a laser sound like? Some
> sources
> > > I've read claim that a sufficiently powerful laser would ionise the air
> > > along its path and produce a "crackle" or "pop" noise, while others
> claim
> > > that regardless of power, a laser has to be of a particular colour to
> ionise
> > > the air and thus produce a sound - but fail to mention what that colour
> is.
> > > Is any of this information accurate?
> > >
> > > As a follow-up question, if a laser actually can make noise, is there an
> > > easy way to derive an approximate relationship between how powerful the
> > > laser is and how loud it is?
> > >
> > > Thanks,
> > >
> > > - David Prokopetz.
> >
> > At high instantaneous laser powers the ossilating electric field in
> > the beam can ionize gasses, including air. An easy way to
> > experimentally investigate this is to bring a laser beam to a focus in
> > gasses of varying pressures. Vary both the gas pressure and focal
> > length of the lens. Longer lens focal lengths result in lower
> > electric fields at the focus. It will be necessary to use a pulsed
> > laser with short pulse lengths as this maximizes the instantaneous
> > electric field.
> >
> > The sound of the electric breakdown is a loud crack.

Relevant Pages

  • Re: The sound of a laser.
    ... what does a laser sound like? ... > I've read claim that a sufficiently powerful laser would ionise the air ... If the electrons in the "air" atoms are able to absorb light energy ... which may absorb or scatter the light as they drift into a continuous beam. ...
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  • Re: The sound of a laser.
    ... A few mJ is enough for air breakdown from a low f/ number focused Q-switched ... there is the sound of the caps discharging. ... >> At high instantaneous laser powers the ossilating electric field in ... >> electric field. ...
    (sci.physics)
  • Re: The sound of a laser.
    ... > I've read claim that a sufficiently powerful laser would ionise the air ... mechanism for a laser to ionize air. ... crackling sound. ...
    (sci.optics)
  • Re: The sound of a laser.
    ... > I've read claim that a sufficiently powerful laser would ionise the air ... mechanism for a laser to ionize air. ... crackling sound. ...
    (sci.physics)
  • Re: The sound of a laser.
    ... > I've read claim that a sufficiently powerful laser would ionise the air ... a laser has to be of a particular colour to ionise ... > the air and thus produce a sound - but fail to mention what that colour is. ... At high instantaneous laser powers the ossilating electric field in ...
    (sci.physics)