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Re: light meters
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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Light Meters
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To: Aquatic-Plants at actwin_com
Subject: Re: Light Meters
From: busko at stsci_edu (Ivo Busko)
Date: Fri, 1 Sep 2000 08:39:31 -0400 (EDT)
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"Wayne Jones" <waj at mnsi_net> wrote:
<snip>
> Averaging the the readings won't do it. The actual amount of light would
> always be higher than the highest reading obtained with a flat detector.
For
> a flat detector the amount of light the detector is able to measure is
> proportional to the cosine of the angle of incidence of the light.
<snip>
Ivo wrote:
But the detectors we are ultimately interested in, the plant's leaves, are
not cosine-corrected. They are, on first approximation, flat surfaces, that
can orient themselves at random angles. So taking a set of readings with a
flat detector oriented at random angles and averaging them, gives IMO a good
estimate of what level of ligth the plants actually "see".
I reply:
Many aquatic plants appear to be adapted to collect low angle light. The
leaves do tend to orient themselves but mostly they are not large flat
surfaces. Limnophila for example, has rod shaped leaves where it doesn't
matter where the light is coming from and sword plants have leaves that grow
in all sorts of directions. It looks to me that light falling from any angle
on a patch of tenellus can be gathered by the plant. I don't think much
light escapes from a dense patch of tenellus.
Wayne