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DPRG: sunlight test data

Subject: DPRG: sunlight test data
From: Alan Bredon abredon at imagin.net
Date: Thu Mar 4 15:16:09 CST 1999

David Philip Anderson wrote:
> All measurements are in Ohms.  Smaller numbers means brighter light.
> ----------------------------------------------------------------------
> CdS Readings Taken Through a 3mm Aperture for Three Different Sources.
> ----------------------------------------------------------------------
> Source          Distance        No-filter       Red     Blue    UV
> ----------------------------------------------------------------------
> 100 watt
>   light bulb    12 inches       380             630     760     1320
> ----------------------------------------------------------------------
> Laser Pointer   12 inches       150             160     360      600
> ----------------------------------------------------------------------
> Sunlight at
>   9:30 am       93 million mi    80             140     120      300
> ----------------------------------------------------------------------

Thanks for the experiment.  It's just so satisfying to eliminate endless
speculation with a good trip to the lab!

I'm bewildered, however, by the filtered responses.  The laser pointer
should have fairly pure 650nM light that has almost no UV.  If so then
why did the laser response change dramatically through the UV filter? 
Why didn't the blue filter block it altogether?  The sunlight makes
sense, because it consists of fairly equal proportions of the spectrum. 
The 100W light appears to have more UV than I  expected, too.

Were these tests performed in a darkened room or fluorescent lit?  Was
the UV filter really a "nothing but UV"?  If it was a UV blocker then
unless it had a 1 stop neutral density, I just don't understand it.  Did
you allow the CDS cell to dark stabilize between tests.  It should rest
to the same value before each new test.

Please help! I'm severely confused!

At any rate, unless a kid maliciously shines a laser pointer into a
captive victim's eye at point blank range for an extended time, I agree
that there is virtually no real possibility of damage to the eye from
casual use at long range past 1 meter.  (I was a Product Safety Engineer
for 10 years!)
The only danger I can think of would be to the next kid I catch screwing
around with his pointer at a movie I paid good money to see!

- --   _  _     Regards, Alan Bredon
    / || \     
   /  ||  \   My views & opinions do not represent my employer. 
  /. .||. .\  "PC means Personal Computer, Political Correctness
 /-|-||||-|-\            will not be tolerated."
  _|_|__|_|_  http://www.imagin.net/~abredon/robot.htm 
 | . .  . . | And always remember to ESCHEW OBFUSCATION! 


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