Re: Light levels and distances

["S. Hieber" <shieber at yahoo_com>]

Wright Huntley and Bill have been discussing variations in light
intensity as a funciton of distantce from the the source:

 
> > Lux, or illuminance per square meter, varies dramatically with the
> distance 
> > from the light source, inversely by the square of the distance, as
> a matter 
> > of fact.  It can almost disappear at the bottom of a deep tank.  
> 
> 
> This statement is far from true, but has become an unfortunate part
> of 
> aquarium mythology.
> 
> The inverse-square law applies only to point sources in an
> environment 
> without any "guiding." Neither is at all true of most aquarium
> situations.

Even if the formula is not "the delta of light intensity = delta in the
inverse square of the distance," it's darker father from the bulb --
eyes can tell and many plants certainly behave differently, just as if
they have more light, when they are closer to bulb.  Line sources of
light, like flourescents, and points sources like MHs are brightest
next the source.


BTW, are there *fortunate* parts of aquarium mythology -- other than
George Booth's fancifully shocking incident a few years ago?  ;-)

Scott H.

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