illumination curve


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h07illuc.gif (1462 bytes)A lamppost will give the most light directly under the lamp. The illumination will decrease when you move away from the light source. This relation is shown by a curve, which I give the name illumination curve.

When the lamp gives light homogenous in all directions, the light stream for each unit of area is inversely proportional with r2. For a sloping bundle of light the light stream is proportional with the cosine of the angle α.
Now setting the light stream at the source to 1, as well as the height from the lamp to the ground, gives the equation above.

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