My red laser pointed 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. . . . "
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Ludwik Kowalski, a retired physics teacher and an amateur journalist.
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