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Diffusion affects the color of objects in a substantial manner because it determines the average path of light in the material, and hence to which extent the various wavelengths are absorbed.<ref>Paul Kubelka, Franz Munk (1931), ''Ein Beitrag zur Optik der Farbanstriche'', Zeits. f. Techn. Physik, '''12''', 593–601, see [https://web.archive.org/web/20110717155703/http://web.eng.fiu.edu/~godavart/BME-Optics/Kubelka-Munk-Theory.pdf ''The Kubelka-Munk Theory of Reflectance''] {{webarchive|url=https://web.archive.org/web/20110717155703/http://web.eng.fiu.edu/~godavart/BME-Optics/Kubelka-Munk-Theory.pdf |date=2011-07-17 }}</ref> Red ink looks black when it stays in its bottle. Its vivid color is only perceived when it is placed on a scattering material (e.g. paper). This is so because light's path through the paper fibers (and through the ink) is only a fraction of millimeter long. However, light from the bottle has crossed several centimeters of ink and has been heavily absorbed, even in its red wavelengths.
And, when a colored object has both diffuse and specular reflection, usually only the diffuse component is colored. A cherry reflects diffusely red light, absorbs all other colors and has a specular reflection which is essentially white (if the incident light is white light). This is quite general, because, except for metals, the reflectivity of most materials depends on their [[refractive index]], which varies little with the wavelength (though it is this variation that causes the [[chromatic dispersion]] in a [[Prism (optics)|prism]]), so that all colors are reflected nearly with the same intensity
==Importance for vision==
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