re: LED Fixtures: Great energy savings, but they could be costing you sleep...

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I had no idea that Kelvins were used to measure something like that

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Kelvins are really a measure of temperture (it's the Celsius scale where zero is absolute zero instead of the freezing point of water) but I believe this is related to blackbody radiation.

Basically, any object that is heated emits energy in the form of light waves, and the light frequency is shorter the hotter the object gets. For example, a stove eye might be a dull red, but something much hotter will be yellow.

In lighting, colors are rated by the temperature a blackbody emitter would have to be to emit that color of light.

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