How Everything Works
How Everything Works How Everything Works
 

QUESTIONS AND ANSWERS
 
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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