| 单词 | principal section |
| 释义 | > as lemmasprincipal section principal section n. Crystallography the cross-section of a crystal containing its optic axis and the direction of a given ray of light. ΚΠ a1830 J. F. W. Herschel Light in Encycl. Metrop. (1845) IV. 516 The section A, then, (which..we will call the principal section of the mica plate,) is characterised by two remarkable lnes..along which, if a polarized ray be incident, its polarization will not be disturbed by the action of the plate. 1910 Encycl. Brit. I. 57/1 One [focal line] lies in the plane containing the principal ray and the axis of the system, i.e. in the ‘first principal section’ or ‘meridional section’, and the other at right angles to it, i.e. in the second principal section or sagittal section. 1976 Social Stud. Sci. 6 147 The orientation of these sides with respect to the crystal axis would determine whether the ray..became polarized parallel to or perpendicular to the principal section of the crystal. < as lemmas |
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