| 单词 | critical angle |
| 释义 | > as lemmascritical angle critical angle n. Optics the angle of incidence at which a ray of light must strike an interface with a less dense medium so as to be refracted parallel to the interface.A ray of light incident at an angle greater than the critical angle is totally reflected. ΚΠ 1829 H. Coddington Treat. Reflexion & Refract. Light ii. 47 in System of Optics I. The angle of incidence for a right angle of emergence is called the critical angle, because it separates or decides between the phænomena of reflexion and refraction. 1966 R. Webster Pract. Gemmol. (ed. 4) vi. 55 The angle of incidence which gives an angle of refraction of 90° is termed the critical angle and is usually denoted by the Greek letter theta θ. The critical angle determines the beginning of total internal reflection. 2005 P. G. Read Gemmology (ed. 3) ix. 82 Rays of light passing through the dense medium of the prism will be reflected back from the surface of the gemstone over an arc of incident angles greater than the critical angle. < as lemmas |
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