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# Physics/Qualities of light

Question
Are amplitude and frequency the only real qualities of light? I have LED lights in my room and I keep thinking to myself that the lighting feels so sterile. And back before the environmental cork screw bulbs lighting seemed more alive. What differences are there with light?

The effect you feel -- sterility -- may be more a matter of frequency than you realize.
Incandescent bulbs seem "warmer" because they ARE warmer. They emit infra-red light, and the visible light they emit has (1) a peak closer to red light and (2) a broader spectrum of frequencies. Your LED lighting gives no IR, is more "blue" than incandescent, and has a far more narrow spectrum of light. It gives the same total amount of visible light (ie, the same number of lumens), but the frequency is different. In that sense, it's less like sunlight, which we as a species consider more (well, how else to say it?) natural.

Solar spectrum

Incandescent light spectrum
http://www.phpwebscripting.com/phpwebsite/images/floodcam_mod/incandescent_spect

White LED spectrum
http://ledmuseum.candlepower.us/sixteen/nfhbed.gif

There is another factor that MIGHT be causing a sense of sterility. As you may be aware, the electricity reaching your home goes between plus 115 volts, then zero, then minus 115 volts, then back to zero, and finally returning to plus 115 volts -- making a full cycle sixty times a second (ie, 60 Hz). An incandescent bulb does not grow dim every 1/60th of a second, it just can't cool down that fast. An LED (and also fluorescent lamps) can, however, grow dim that quickly. Thus, there is a mild flicker effect with both LEDs and fluorescent bulbs. Most people have no problem with this; for others, it's a problem. Again, it just seems un-natural.

So you are not imagining something when you get a sense of sterility. But the effect IS based almost entirely on the frequency spectrum.
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Physics

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B.A. in Physics (with honors) from University of California at Berkeley.M.A. in Physics (with honors) from University of Texas Austin.