| 释义 |
opacity|əʊˈpæsɪtɪ|
[a. F. opacité (15–16th c. in Hatz.-Darm.), ad. L. opācitās, f. opācus opaque.]
The quality or fact of being opaque; opaqueness.
1. a. The state of being in shadow; darkness, dimness, obscurity; also, an instance of this.
1611Cotgr., Opacité, opacitie, shadinesse, vmbrage [etc.]. 1646Sir T. Browne Pseud. Ep. vi. x. (1686) 263 Others ascribe these causes to the graduality of Opacity and Light. 1656S. H. Gold. Law 103 Artificial Opticks..to amplifie thy sight, and dispel Opacity. a1763Shenstone Ess. (1806) 3 He renders the opacity of the other more discernible. 1807Knox & Jebb Corr. I. 358 When the soul emerges from the opacities of this mortal life. 1812G. Chalmers Dom. Econ. Gt. Brit. Pref. 13 The glimmering of the faintest dawn is more invigorating than the gloom of total opacity.
b. The condition of not reflecting light.
1794G. Adams Nat. & Exp. Philos. II. xxi. 402 Opacity..[in one sense] signifies want of transparency; in the latter, that no light comes from the body. 1862Tyndall Mountaineer. ix. 75 It was most interesting to observe..tree after tree losing its opacity and suddenly robing itself in glory.
2. a. The quality or condition of being impervious to light: opposed to transparency or translucency; spec. the ratio of the intensity of the light incident on a sample or object to that of the light transmitted by it.
1634Peacham Gentl. Exerc. iii. 139 As Cristall, Ice, &c. by reason of their perspicuitie..so are Quicksilver, Silver, Lead, Steele, Iron, Tin, and the like, by reason of their opacity. 1638Wilkins New World i. (1684) 102 An Orb of thick Vaporous Air..though it have not so great Opacity, as to terminate the Sight. 1750tr. Leonardus' Mirr. Stones 35 Perspicuity, or opacity, occasion many differences in stones. 1796Home in Phil. Trans. LXXXVII. 9 A lady who had lost the sight of both [eyes], by opacities in the crystalline lenses. 1814A. Aikin Man. Min. Introd. 31 When the passage of light is entirely stopped opacity comes on. 1885Chamb. Jrnl. II. 140/2 The..milk-tester which..owes its efficiency to the relative opacity of pure milk and milk and water. 1890Hurter & Driffield in Jrnl. Soc. Chem. Industry 31 May 455/2 The inverse of that fraction, or I/Ix = eka measures the opacity of the substance. 1926J. W. T. Walsh Photometry xiii. 392 The opacity is then measured by placing the exposed area of the plate between a source of light and a photometer. 1939Q. Jrnl. Meteorol. Soc. LXV. 417 In the case of five stations..the summer values of opacity are higher than the winter values, owing to the prevalence of sea fogs in summer. 1966R. J. Ross Television Film Engin. iv. 169 The silver deposit and the opacity are so related that the logarithm of the opacity is directly proportional to the mass of silver.
b. transf. acoustic opacity, imperviousness to waves of sound. Also used with reference to other forms of radiation.
1871Tyndall Fragm. Sc. (1879) I. x. 331 Here we had the acoustic opacity of the air. 1878Smithsonian Rep. 510 In the cases of acoustic opacity..if he had simultaneously made observations in an opposite direction, he would have come to a different conclusion. 1928[see Lipiodol]. 1971Jrnl. Electron. Microsc. XX. 124/1 The pronounced electron opacity was localized especially..on the outer membrane.
3. fig.
a. Darkness or obscurity of meaning.
b. Mental or intellectual dullness; denseness or obtuseness of intellect; concr. one in whom this is embodied.
α1560Rolland Crt. Venus ii. 497 Sa full thair warkis was of opacitie [ed. 1884 pr. oporcitie].
β1640Bp. Hall Serm. 1 John i. 5, Wks. 1837 V. 421 That gloomy and base opacity of conceit, wherewith our earthly minds are commonly wont to be overclouded. a1677Barrow Serm. Wks. 1716 III. 375 No Discourse could..penetrate those Opacities of Ignorance. 1837Carlyle Misc. Ess., Mirabeau (1872) V. 202 Natural opacity being so doubly and trebly darkened by accidental difficulty and perversion. 1844― Misc. (1865) IV. 297 The Opacities have been pleased to suppress this election. 1874L. Carr Jud. Gwynne I. iv. 111 A light dawned through the thick opacity of his brain.
c. With reference to a rule in Phonology: the state or quality of being opaque (sense 3 c).
1971[see opaque a. 3 c]. 1975Trans. Philol. Soc. 1974 113, I have myself argued..that for French the elegance of such a solution is outweighed by its disadvantages and that restructuring occurred when generalization of the loss of word-final [ə] made for opacity: the conditioning of denasalization before an intervocalic nasal was no longer discernible from surface phonetic shapes. 1977Language LIII. 19 In each instance of opacity, a phonological rule which relates a large number of surface lexical items is obscured by the presence of other items in which the rule appears to fail. |