From: "Bob May" 
To: "atmlist" 
Reply-To: "Bob May" 


The polarizers can be any distance from the glass, including contact with
it.  The light source needs to be far enough away to somewhat evenly
illuminate a fair part of the glass.  You don't want to be searching across
the glass with the flashlight in contact on the other side, do you?  Even a
cloudy sky is a good source of the light needed for the test and the test
can be done in bright sunlight as you are looking through the glass at the
light source and seeing differences in brightness of that light passing
through.  Don't even bother to block off any lights as the results of
looking through the glass are quite dramatic enough that you won't have any
problem seeening the results.
I will note that I've seen the brightness changes on a side window of a
fairly new car window (don't remember the model but I then went to another
different car and saw the same thing again) from a reflection off of the
window of the sky while wearing polaroid sunglass covers for my spectacles.
It looked like somebody spray painted bright and dark spots on the window
to about 1/2 of the light reflected off of the window.  The windows were
the single piece windows rather than the two layers of glass with the
plastic between.
Bob May
http://nav.to/bobmay
bobmay{at}nethere.com
NEW! http://bobmay.astronomy.net

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