How Everything Works
How Everything Works How Everything Works

Question 1024

How do the spectrums of different light sources differ? For example, when you look at an incandescent bulb through a spectroscope, do you see colors other than what you see when you look at a fluorescent bulb? — EC, Tokyo, Japan
The spectrum of light from an incandescent bulb is what is known as a blackbody thermal spectrum—the light produced by a hot object. A blackbody spectrum is relatively featureless—you can't even tell what material is producing the light; only what temperature it has. All the wavelengths of light are present in thermal radiation and their intensities vary smoothly with wavelength. For the filament temperature of a normal incandescent bulb, the reds are brighter than the greens and the blues are rather weak.

A fluorescent bulb pieces together white light out of several separate colored lights. The spectrum of light from a fluorescent lamp is not simple or featureless—many wavelengths are essentially missing and the intensities of the remaining wavelengths don't vary smoothly with wavelength. Viewed through a spectroscope, the light from a fluorescent light has many bright bands of color interspersed with relatively dark bands.


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