From: "JACK L. URETSKY (C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE, IL 60439" <JLU@HEP.ANL.GOV>
Date: Sun, 13 Jun 1999 08:27:56 -0500
Hi Scott-
You ask:
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Also, while I'm at it, am I correct in saying that the dark adapted eye
responds to around five visible light photons per second striking a given
receptor cell?
Many thanks in advance.
Scott.
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I recall that in 1954, while I was spending half-a-year at Texas
Instuments, I worked on a problem related to geophysical prospecting from
an airplane by looking for resonance fluorescence. At the time I settled
on order of magnitude of one photon as the threshold for detection.
Now, however, I wonder how one makes the measurement. A 1942
experiment with weak light flashes gave a response curve with a 10%
probability of seeing the flash at the 5 photon level. The curve is
reproduced in Hobbie, <Intermediate Physics for Medicine and Biology>
(3rd Ed., 1997) at p. 375.
Regards,
Jack
"I scored the next great triumph for science myself,
to wit, how the milk gets into the cow. Both of us
had marveled over that mystery a long time. We had
followed the cows around for years - that is, in the
daytime - but had never caught them drinking fluid of
that color."
Mark Twain, Extract from Eve's
Autobiography