Asked by  | 10th Mar, 2009, 11:29: AM

Expert Answer:

The light from a point light source spreads out uniformly in all directions. The intensity at a given distance r from the light = (power output of the light  source/ surface area of the sphere). Since the area of a sphere varies as the square of its radius r, the intensity will vary as 1/r2.

If the distance is doubled, the intensity becomes one-fourth.

Answered by  | 13th Mar, 2009, 04:07: PM

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