A diffraction grating reveals the composition of light. There is a lot of information contained within the spectrum that our eyes cannot detect. Understanding how the psectrum is related to the sensation of color makes it easier to understand color effects.
Diffraction gratings separate light into its components
in a way that depends directly on the fact that
light is a wave; the amount of deflection of the
light depends on its wavelength. The color effects
of the blue of the sky, an oil slick, a soap film,
a butterfly's wings, and in light viewed through
a finely woven cloth or a feather are all diffraction
effects.
When atoms and molecules are placed in a spark or a flame, they emit light with a spectrum that is specific to the material: it is a "fingerprint", by which the type of atom or molecule can be determined. Astronomers learn the composition of stars by looking at their spectra (the first evidence for the existence of the element helium came from a study of the spectrum of the sun). Chemists use spectroscopy to analyze the chemical composition of materials.
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This sign uses two light sources
with different spectra. The word "OPEN" is spelled in neon, and the frame is in mercury spectrum. |
This light contains a kind of fluorescent
lamp, that only emits certain colors of light. We see the light, and then its violet, blue, green, and red images -- and then this is repeated. |
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