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Re: Light intensity
Wright Huntley points out:
>In free space, radiation falls off in intensity as the inverse square of the
>distance from a limited source (point).
And I add:
In practical terms, you can figure how much light you lose with distance:
* fluorescent tubes are linear sources and light falls off roughly inversely
proportional to distance - twice as far, 1/2 the light.
* metal halide bulbs are close to points sources and light falls off roughly
proportional to the square of the distance - twice as far, 1/4 the light.
I measures these effects with my trusty Lux meter.
This assumes that the relector is NOT perfect and is NOT directing all the light
towards the target. A really good reflector will greatly corrupt the simple
relations described above.
And, as Wright further points out, all bets are off once the light gets in the
water. I also measured this in a 29 gallon tanks the results were bizarre. My
website has some details under lighting.
George Booth in Ft. Collins, Colorado (booth at frii_com)