Re: [Phys-l] A demo for biologists?

[ludwik kowalski <kowalskil@mail.montclair.edu>]

Thanks Brian.
I have performed this "thin wedge of air" demo, and Newton rings"  
demo, many times in the past. But I was not able to realize that  
Bernard was referring to this kind of fringes. Should I blame my old  
brain or should I blame absence of clarity in his explanation?
Ludwik


But Bernard's message was not
On May 17, 2009, at 12:24 PM, Brian Whatcott wrote:

> I think this is what Bernard intended to describe, but was fearful to
> appear to be talking down to you or perhaps he felt you were  
> unworthy of
> his time and effort:
>
> take two fresh microscope slides and set a  1 cm wide strip of saran
> wrap across one short end on one slide, then sandwich it with a  
> second,
> in hopes of leaving a very thin wedge of air between two slides.
> Optionally tape together both short ends of the sandwich.
>
> Illuminate the slides with an expanded laser beam, a filtered beam  
> from
> a compact fluorescent light fitting or a plain fluorescent.
> Look carefully through the slide sandwich and you will see faint  
> stripes
> - if the preparation was particularly careful, you will see the  
> stripes
> across the short dimension progressing towards the saran sliver.
>
> Brian W
>
>
> ludwik kowalski wrote:
> > Dear Bernard,
> >
> > What is CFL? What is this "it" that you tried? Did you use an
> > interferometer? If not then why do you think that fringes have
> > anything to do with your saran wrap?
> >
> > Ludwik, who is often confused by telegraphic style, and by acronyms
> > with which he is not familiar.
> >
> >
> > On May 17, 2009, at 12:31 AM, Bernard Cleyet wrote:
> >
> >
> > > Aaagh -- not a microscope,  microscope slides.   I just tried it w/
> > > saran wrap.  (0.0003"** = ~ 7.6 microns)   This is ~ 13 wavelength.
> > > So ~ 26*** fringes over very ~ 3"  (v.~ 7 cm);  easily counted w/ a
> > > magnifying glass, or unaided if equi-spaced.  Won't be as the glass
> > > isn't stiff.
> > >
> > > I didn't count them, as I was hand holding it and the beam was not
> > > wide enuff.  I also saw them (multicolored) with a CFL.  Using a CFL
> > > and a green filter would be good.  A kitchen physicist would use
> > > green food coloring in a glass of water?
> > >
> > > ** Measured with a 0.0001" X 0.050"  Mitutoyo Dial Thickness Gauge.
> > > ***Assuming no Sr. moment.
> > >
> > > bc
>
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Ludwik Kowalski, a retired physics teacher and an amateur journalist.  
Updated links  to publications and reviews are at:

http://csam.montclair.edu/~kowalski/cf/   http://csam.montclair.edu/~kowalski/my_opeds.html 
   http://csam.montclair.edu/~kowalski/revcom.html

Also an ESSAY ON ECONOMICS at: http://csam.montclair.edu/~kowalski/economy/essay9.html