hey choader,,,light, like any electromagnetic radiation, (from an isotropic source) decays according to the inverse square law. "the intensity per unit area varies in inverse proportion to the square of the distance", or E=I/dē.
so if you double the distance, you reduce the intensity to one-fourth.
now, that doesn't hold entirely true if you have a reflector, especially a good one, behind your lamp, and you're trying to measure (or approximate) the intensity close to it. then the geometry of the reflector becomes very important, and it's easier to just measure the light.
hope that helps?
Last edited by JoseHempSeed : 07-20-2002 at 07:40 PM.
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