“diffraction”的概念、定义、翻译、参考文献-科学参考

diffraction

Physics

The spreading or bending of waves as they pass through an aperture or round the edge of a barrier. The diffracted waves subsequently interfere with each other (see interference) producing regions of reinforcement and weakening. First noticed as occurring with light by Francesco Grimaldi (1618–63), the phenomenon gave considerable support to the wave theory of light. Diffraction also occurs with streams of particles because of the quantum-mechanical wave nature of such particles. See also Fresnel diffraction; Fraunhofer diffraction; electron diffraction.

Astronomy

The slight bending of light around the edge of an obstacle in its path. It is a consequence of the wave nature of light. Because of diffraction, a star image consists of an Airy disk surrounded by several diffraction rings, produced by diffraction at the edge of the telescope lens or mirror. In a reflecting telescope which has a secondary mirror supported by one or more arms, diffraction around the arms causes the images of stars to have spikes. Diffraction also occurs at other wavelengths, such as radio. A point radio source occulted by the Moon, for example, disappears or reappears with brightness oscillations, rather than abruptly, as a diffraction pattern sweeps across the observatory. The size of the diffraction pattern increases with the wavelength of the radiation involved.

Chemistry

The bending or spreading of waves as they pass around an obstacle, resulting in interference. If the wavelengths of the waves being diffracted are roughly the same as the distances between atoms in a molecule or solid, then information can be obtained about that molecule or solid. Important examples of diffraction in chemistry are electron diffraction, LEED, neutron diffraction, and X-ray diffraction.

Electronics and Electrical Engineering

A phenomenon occurring when electromagnetic waves or beams of charged particles, such as electrons, encounter either an opaque object or a boundary between two media. The beams are not propagated strictly in straight lines but are bent at the discontinuity. This effect is due to the wave nature of electromagnetic radiation and the de Broglie waves associated with the charged particles. Interference between the diffracted waves produces a diffraction pattern of maxima and minima of intensity; the diffraction pattern produced depends on the size and shape of the object causing the diffraction and the wavelength of the incident radiation. It can be used to investigate crystal structures or surface structures.
Electron and X-ray diffraction are employed to investigate crystal structures, the diffraction pattern produced being dependent on the spacing of the crystal planes. Electron diffraction is used to assess the structure of a crystalline semiconductor material near the surface. Low-energy electron diffraction uses a beam of low-energy electrons incident normal to the surface and the diffraction patterns from the back-scattered electrons are detected. Reflection high-energy electron diffraction uses a high-energy electron beam at a very small grazing angle of incidence. In this case the forward-scattered electrons produce the diffraction pattern. Electron diffraction patterns obtained from transmission electron microscopy can be used to provide information about crystalline materials throughout their bulk but this latter is a time-consuming method and very difficult to interpret.
X-ray diffraction is employed to detect imperfections in semiconductor crystals by means of X-ray topography, using a slit and photographic plate to record a ‘map’ of the slice on a photographic film. Although lateral resolution is of the order of several micrometres the technique is rapid and nondestructive.

Geology and Earth Sciences

The radial scattering of any wave (light, radio, seismic, water, etc.) incident upon an abrupt discontinuity in accordance with Huygens’ principle. A fault plane, angular unconformity, small isolated objects (e.g. boulders, fragments of wrecked ships, etc.) will all give rise to the diffraction of incident seismic energy. The quasi-hyperbolic curvature of a seismic diffraction event is related to the velocity within the media through which the diffracted wave travels. In media with slow velocities, the hyperbola is strongly curved, the curvature decreasing as velocity increases.

单词	diffraction
释义	diffraction Physics The spreading or bending of waves as they pass through an aperture or round the edge of a barrier. The diffracted waves subsequently interfere with each other (see interference) producing regions of reinforcement and weakening. First noticed as occurring with light by Francesco Grimaldi (1618–63), the phenomenon gave considerable support to the wave theory of light. Diffraction also occurs with streams of particles because of the quantum-mechanical wave nature of such particles. See also Fresnel diffraction; Fraunhofer diffraction; electron diffraction. Astronomy The slight bending of light around the edge of an obstacle in its path. It is a consequence of the wave nature of light. Because of diffraction, a star image consists of an Airy disk surrounded by several diffraction rings, produced by diffraction at the edge of the telescope lens or mirror. In a reflecting telescope which has a secondary mirror supported by one or more arms, diffraction around the arms causes the images of stars to have spikes. Diffraction also occurs at other wavelengths, such as radio. A point radio source occulted by the Moon, for example, disappears or reappears with brightness oscillations, rather than abruptly, as a diffraction pattern sweeps across the observatory. The size of the diffraction pattern increases with the wavelength of the radiation involved. Chemistry The bending or spreading of waves as they pass around an obstacle, resulting in interference. If the wavelengths of the waves being diffracted are roughly the same as the distances between atoms in a molecule or solid, then information can be obtained about that molecule or solid. Important examples of diffraction in chemistry are electron diffraction, LEED, neutron diffraction, and X-ray diffraction. Electronics and Electrical Engineering A phenomenon occurring when electromagnetic waves or beams of charged particles, such as electrons, encounter either an opaque object or a boundary between two media. The beams are not propagated strictly in straight lines but are bent at the discontinuity. This effect is due to the wave nature of electromagnetic radiation and the de Broglie waves associated with the charged particles. Interference between the diffracted waves produces a diffraction pattern of maxima and minima of intensity; the diffraction pattern produced depends on the size and shape of the object causing the diffraction and the wavelength of the incident radiation. It can be used to investigate crystal structures or surface structures. Electron and X-ray diffraction are employed to investigate crystal structures, the diffraction pattern produced being dependent on the spacing of the crystal planes. Electron diffraction is used to assess the structure of a crystalline semiconductor material near the surface. Low-energy electron diffraction uses a beam of low-energy electrons incident normal to the surface and the diffraction patterns from the back-scattered electrons are detected. Reflection high-energy electron diffraction uses a high-energy electron beam at a very small grazing angle of incidence. In this case the forward-scattered electrons produce the diffraction pattern. Electron diffraction patterns obtained from transmission electron microscopy can be used to provide information about crystalline materials throughout their bulk but this latter is a time-consuming method and very difficult to interpret. X-ray diffraction is employed to detect imperfections in semiconductor crystals by means of X-ray topography, using a slit and photographic plate to record a ‘map’ of the slice on a photographic film. Although lateral resolution is of the order of several micrometres the technique is rapid and nondestructive. Geology and Earth Sciences The radial scattering of any wave (light, radio, seismic, water, etc.) incident upon an abrupt discontinuity in accordance with Huygens’ principle. A fault plane, angular unconformity, small isolated objects (e.g. boulders, fragments of wrecked ships, etc.) will all give rise to the diffraction of incident seismic energy. The quasi-hyperbolic curvature of a seismic diffraction event is related to the velocity within the media through which the diffracted wave travels. In media with slow velocities, the hyperbola is strongly curved, the curvature decreasing as velocity increases.
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