Readers Write: Seeing the light on LED lights

With all the arguing over light sources one crucial fact has escaped mention. Common to all sources is that light intensity obeys the inverse-square law.  Intensity 10 feet from a source is consequently a hundredth that at one foot away. At 30 feet away, intensity is reduced by a factor of 900.

Based on this relationship, a person is likely exposed to a lot more blue light from computer or television use, even from LED headlights of oncoming motorists, than from an LED lamppost.

Len Mansky


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