| 释义 |
diffraction|dɪˈfrækʃən|
[ad. mod.L. diffractiōn-em (Grimaldi 1665), n. of action from diffringĕre: see prec. So F. diffraction 1666 in Hatz.-Darm.]
1. Optics. The breaking up of a beam of light (in the case of monochromatic light) into a series of light and dark spaces or bands, or (in that of white or other composite light) of coloured spectra, due to interference of the rays when deflected from their straight course at the edge of an opaque body or through a narrow aperture or slit.
(These phenomena were formerly denoted by the name inflexion; cf. also deflexion 5.)
1671Phil. Trans. VI. 3068 Light is propagated..also by diffraction..when the parts of Light, separated by a manifold dissection, do in the same medium proceed in different ways. 1803Young Ibid. XCIV. 13 The observations on the effects of diffraction and interference. 1830Herschel Stud. Nat. Phil. iii. ii. (1838) 252 The diffraction or inflection of light, discovered by Grimaldi, a Jesuit of Bologna. 1855H. Spencer Princ. Psych. (1872) II. vi. xi. 138 Only on the theory of undulations can..diffraction be accounted for. 1860Tyndall Glac. i. xxii. 154 All the hues produced by diffraction were exhibited in the utmost splendour. 1878J. D. Steele Physics 126 If we hold a small needle close to one eye and look toward the sun we see several needles. This is caused by diffraction.
b. Acoustics. An analogous phenomenon occurring in the case of sound-waves passing round the corner of a large body, as a house.
2. In etymol. sense: Breaking in pieces, breakage. nonce-use.
1825Coleridge Aids Refl. (1848) I. 286 There being..no facts in proof of the contrary, that would not prove equally well the cessation of the eye on the removal or diffraction of the eye-glass.
3. attrib. (in sense 1), as diffraction band, diffraction fringe, diffraction spectrum, etc.; diffraction grating, a plate of glass or polished metal ruled with very close equidistant parallel lines, producing a spectrum by diffraction of the transmitted or reflected light.
1863–72Watts Dict. Chem. III. 608 Barton's buttons, which are metallic buttons having very fine lines engraved on their surfaces..exhibit magnificent diffraction spectra. 1867G. F. Chambers Astron. x. iii. (1877) 847 A diffraction grating. 1868Lockyer Guillemin's Heavens (ed. 3) 496 Observing the image of a large star out of focus. If..the diffraction rings are not circular, the screws of the cell should be carefully loosened [etc.] 1873Tyndall Lect. Light ii. 91 The street-lamps..looked at through the meshes of a handkerchief, show diffraction phenomena. 1890C. A. Young Elem. Astron. vi. §193 The essential part of the apparatus [spectroscope] is either a prism or train of prisms, or else a diffraction ‘grating’. |