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



P.S.
The laser pointer is AURORA, Class IIIa product, Model Al31.

On May 15, 2009, at 6:19 PM, ludwik kowalski wrote:

Why didn't I see any contrast on the white wall?

My red laser pointer made a light spot (diameter about 2 cm with
three well separated diffraction fringes around it) on the white wall,
25 meters away. A microscopic slide was half-covered with a "crystal-
clean polyethylene CLINGWRAP." The thickness was probably several
microns (I have nothing to measure the thickness at home). In another
place I had two layers of the same film. But nowhere was I able to see
the expected contrast. What was wrong with my hypothesis?

Ludwik

On May 15, 2009, at 11:00 AM, ludwik kowalski wrote:

". . . Suppose a small piece of glass (a microscopic slide) or plastic
is partially covered with a transparent foil of thin plastic (mylar).
Placing this transparent object into the laser beam would probably
create a contrast (for example, mylar-coated area being darker or
brighter that the other area. Stretching the film (reduction of
thickness) would probably change the contrast. . . . "

- - - - - - - - - - - - - -
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







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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