it always falls off at the same rate. The difference is a florescent tube
is long and narrow, so the 'point' of light is really many points of light.
But the rate of decrease remains the same from each point source of light no
matter what type of lamp produces it. It is an inverse square; so three
feet is 9 times less intense and two feet is 4 times less intense...than the
intensity at the source, and four feet is...?

....and gravity propagates forward at the speed of light. If the sun
disappeared now, the earth would behave as if it had a gravitational body
holding it in orbit for how long?

....and the efficacy of earth made O-Rings and foam insulation on
interstellar space craft can be summed up best by what Simpson-esc buzz
word?

"Duncan" wrote in message
news:c8AKi.90$x%6.65@pd7urf2no...
I still falls off at the same rate.
"
HOWEVER, from a large or diffuse source such as a fluorescent tube,
the falloff is less drastic because the tube is, in effect, a large
number of overlapping point sources. The handy rule for such a source
is that the intensity falls off as the inverse of the distance, i.e.
twice as far ,1/2 as intense, three times as far, 1/3, etc.

J. Del Col