Re: Hearing Light?

["Robert W. Harris" <rwharris@CATH-MEM.ORG>]

From: Michael Edmiston <edmiston@BLUFFTON.EDU>


> I have not tried this yet, but I will.  My first guess is that the
blackened
> membrane itself heats/cools and therefore moves from expansion contraction
> (rather than the enclosed air heating/cooling).

That sounds reasonable to me. There would have to be a time lag before the
air inside could respond.  I'm still surprised that the black plastic
responds so quickly.

> The pickle jar cannot
> appreciably do this because the glass is too thick and rigid.  I continue
> having difficulty believing the air near a blackened surface can heat/cool
> fast enough to respond sufficiently to a small 120-Hz fluctuation in
radiant
> energy.
> I will also try the following if you have not... does a clear or white
> stethoscope membrane produce the hum?



I tried white paper (slightly less stiff than the original black plastic)
and clear plastic transparency material.  No observable hum in either case.

Br. Robert W. Harris
Catholic Memorial High School
rwharris@cath-mem.org
http://www.cmphysics.org

> Michael D. Edmiston, Ph.D.              Phone/voice-mail:
419-358-3270
> Professor of Chemistry & Physics        FAX:
419-358-3323
> Chairman, Science Department            E-Mail
edmiston@bluffton.edu
> Bluffton College
> 280 West College Avenue
> Bluffton, OH 45817
>
>
> Bringing the black membrane of a stethoscope very close to a 7.5 W
> incandescent bulb produced a quite distinct hum in the stethoscope, which
> surprised me.  Moving the stethoscope away, or shielding it with a piece of
> paper proved that the hum was due to the flickering of the bulb.
>
> I'll have to buy a jar of pickles.
>
> I wonder if the stethoscope is a better "matching transformer" than the
tube
> you were using???
>
> Br. Robert W. Harris
> Catholic Memorial High School
> rwharris@cath-mem.org
> http://www.cmphysics.org