Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Change in the directions and intensities of a group of waves after passing by an obstacle or through an aperture whose size is approximately the same as the wavelength of the waves.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The breaking up of an electromagnetic wave as it passes a geometric structure (e.g. a slit), followed by reconstruction of the wave by interference.

from the GNU version of the Collaborative International Dictionary of English

  • n. The deflection and decomposition of light in passing by the edges of opaque bodies or through narrow slits, causing the appearance of parallel bands or fringes of prismatic colors, as by the action of a grating of fine lines or bars.

from The Century Dictionary and Cyclopedia

  • n. In optics, the spreading of light or deflection of its rays, accompanied by phenomena of interference: occasioned by the neighborhood of an opaque body to the course of the light, as when it passes by the edge of an opaque body or through a small aperture, the luminous rays appearing to be bent or deflected from their straight course and mutually interfering with one another. See interference.
  • n. Thus, if a beam of monochromatic light is passed through a narrow slit and received on a screen in a dark room, a series of alternately light and dark bands or fringes is seen, which diminish in intensity and distinctness on either side of the central line; if white light is employed, a series of colored spectra of different orders is obtained. Similar phenomena of diffraction are obtained from diffraction gratings, which consist of a band of equidistant parallel lines (from 10,000 to 30,000 or more to the inch), ruled on a surface of glass or of polished metal; the spectra obtained by this means are called interference or diffraction spectra. They differ from prismatic spectra, since in them the colors are uniformly distributed in their true order and extent according to their difference in wave-length; while in the latter the less refrangible (red) rays are crowded together, and the more refrangible (blue, violet) are dispersed. Diffraction gratings are now much used, especially in studying the solar spectrum. The best gratings are ruled on speculum metal with a concave surface (often called Rowland gratings, after Professor Henry A. Rowland of Baltimore), and give an image of the spectrum directly, without the intervention of a lens.
  • n. Hence In acoustics, the analogous modification produced upon sound-waves when passing by the edge of a large body, as a building.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. when light passes sharp edges or goes through narrow slits the rays are deflected and produce fringes of light and dark bands

Etymologies

New Latin diffrāctiō, diffrāctiōn-, from Latin diffrāctus, past participle of diffringere : dis-, apart; see dis- + frangere, to break; see bhreg- in Indo-European roots.
(American Heritage® Dictionary of the English Language, Fourth Edition)

Examples

  • The one at f22 has a much wider depth of field and the overall loss of resolution due to diffraction is not noticeable at this magnification.

    Archive 2009-06-01

  • The principle of X-ray diffraction is old and was awarded with the Nobel Prize in physics already in 1915.

    Press Release: The 1982 Nobel Prize in Chemistry

  • Although the experiments in diffraction confirm so beautifully the de Broglie-Schrödinger wave theory, the position is less satisfactory as regards the extended theory due to Dirac.

    G.P. Thomson - Nobel Lecture

  • The smallest feature is limited by how small a dot of light you can make with your imaging system, which faces a fundamental limit called the diffraction limit.

    Ars Technica

  • We’ve mentioned above that diffraction is only appreciable when light interacts with objects of size comparable to the wavelength, and this is true of light passing through the slit, as well.

    Optics basics: What is a wave? Part III: Diffraction « Skulls in the Stars

  • The mathematical theory of diffraction is relatively complicated, and requires a significant amount of vector calculus, so we won’t go into too much detail here.

    Optics basics: What is a wave? Part III: Diffraction « Skulls in the Stars

  • The apparent bending of sound waves around corners is an example of diffraction, which is a characteristic behavior of waves encountering an obstacle.

    How to Teach Physics to Your Dog

  • In chemistry, the combination of neutron diffraction, which provides information on the location of atomic nuclei in a molecular crystal, together with X-ray diffraction, which is sensitive to the location of the electrons, gives valuable information on molecular structure.

    Accelerators and Nobel Laureates

  • There is no better instance of Newton's quantitative approach to his experiments than the following undated manu - script page describing things “To be tryed” to elucidate the phenomenon of diffraction, that is the bending of light, and the production of colored fringes (fasciae to Newton), when light passes through a tiny hole or past a knife-edge:

    Dictionary of the History of Ideas

  • The principal on which this separation of light depends is known as diffraction and cannot be explained here, but a similar effect takes place when light falls on the naturally ruled surface of a pearl and helps produce the play of colors known as iridescence.

    A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public

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