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Re: Laser Pointer Intensity -Part 2

At 09:45 6/3/99 -0500, you wrote:
Herb Gottlieb from New York City notes...

(...the intense red beam from a HeNe laser has less
effect on our photometers than the beam of an ordinary flashlight))


I seem to remember working a little calculation that showed a
laser pointer could provide comparable energy intensity
(energy density if you will, or energy per unit cross-section)
to that of the Sun.
But when I control the cross section with a duct tape cover
and pinhole in front of an exposure meter, then make allowance
for the lower actinic effect of red light than the white plus
u/v from the Sun, I STILL find that Herb cannot be readily
contradicted.

Never one to let an adverse experimental result interfere with
a hard earned prejudice, I reran this little test after noticing
that the laser pointer light scattered off its exit port diminished
in a second or so. I installed 3 fresh silver oxide cells.
Then noticing that the photographic light meter gave an indication
in bright sunlight even with its sensing port blocked, I wrapped
the Bewi Super with its white plastic case in an aluminum
foil cover, uncovering only the needle and a pinhole aperture.

Now, I get comparable needle deflections.
However - photographic meters were needed to cover a wide range
of illumination, so critical detection of intensity differences
is not well indicated. (They are now falling into disuse with the
spread of auto exposure cameras, and others with built in exposure
indication.)

brian whatcott <inet@intellisys.net>
Altus OK