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Unit conversion help

Pascal Meunier pmeunier at sgt-peppers.purdue.edu
Thu Aug 21 10:20:17 EST 1997

In article <33F88EFA.8DB3A67E at mail.telepac.pt>, Monica Moura
<mtmoura at mail.telepac.pt> wrote:

> Please forgive me if this is too basic (or off topic) to post here, but
> I wonder if anyone could please help me with this conversion problem I
> have. How can I convert a value that is in lux (illuminance) to
> micromole*m^-2*sec^-1?

Hello Monica,

Have a look at "Plotting rates of Photosynthesis as a function of light
quality" Dean L (1996), the American Biology Teacher vol 58, p.424-426.
What he says is not entirely accurate and the experiments and conclusions
reported there are rather weak (I disagree with several of them), so I do
not recommend this for reading or taking seriously what is said in there.
However, he lists a number of useful references.
Here's a truncated quotation you might find useful:
"If the light source is a tungsten filament, an estimate of the photon
fluence rate in micromol photons m^-2s^-1 can be obtained by dividing the
lux value at a given distance by 50 (Table 3, Thimijan and Heins 1983)"


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