In optics, a spreading out or deflection of a light wave as it passes through an opening or hits an object. A consequence of this is that, if white light is projected through a thin aperture no longer than a few wavelengths wide, the light will spread out on the far side of the aperture, the shorter wavelengths spreading farther than the longer ones. As a result, small grids possessing very small apertures (such as a diffraction grating) cause white light to break down into the constitutent spectral colors. (See Diffraction Grating.) This process has the same effect as that which underlies the principle of the prism, but is a different process. (See also Dispersion.)
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