How Everything Works
How Everything Works How Everything Works

Question 478

How can I differentiate between daylight and incandescent light?
Actually daylight is a form of incandescent light. Incandescent light is the thermal radiation emitted by a hot object such as the filament of a light bulb or the surface of the sun. But the spectrum of incandescent light emitted by an object depends on its temperature. Since the filament of an incandescent light bulb has a temperature of only about 2500° C, its light is much redder than the light emitted by the 6000° C sun. That's why photographs taken indoors with incandescent lighting turn out so orange—the light just isn't white, it's orange-red. So you can differentiate between sunlight and the light from an incandescent bulb by comparing the spectrums. Look for the relative intensities of red, green, and blue lights. Sunlight will have much more blue in it than light from an incandescent bulb.

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