| diffraction | When a wave train passes an obstacle secondary waves are set up that interfere with the primary wave and give rise to bands of constructive and destructive interference. Around a point source of light, in consequence, is a series of concentric light and dark bands (coloured bands with white light), a diffraction pattern. (18 Nov 1997) |
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| diffraction grating | <microscopy> An artificially produced periodic array of scattering centres capable of producing a pattern of diffracted energy, such as accurately ruled lines on a plane surface. (05 Aug 1998) |