| 单词 | nodal point |
| 释义 | > as lemmasnodal point nodal point n. (a) (see senses 1a, 3); (b) Optics either of two points on the optic axis of a lens or lens system such that the straight line joining one of them to a point on the object is parallel to the line joining the other to the corresponding point on the image. ΘΚΠ the world > movement > absence of movement > [noun] > suspense of movement > point or line of rest in oscillating body nodal pointa1830 nodea1830 a1830Nodal point [see sense 1a]. 1880 J. Le Conte Sight 29 This point of ray-crossing is called the nodal point. 1962 H. C. Weston Sight, Light & Work (ed. 2) i. 5 This line is the optic axis, and on it lies the optical centre of the refracting system, called the nodal point. 1977 J. Hedgecoe Photographer's Handbk. 336/3 Nodal points are used for optical calculations, e.g. to calculate focal length. nodal point a. Designating a line, point, or surface of absolute or comparative rest in a standing wave system; (Mathematics) designating a point or points at which a spherical harmonic or similar periodic function has the value zero. Also in extended use. Chiefly in nodal point. ΚΠ a1830 J. F. W. Herschel Sound in Encycl. Metrop. (1845) IV. 782 Such points of rest are called nodes or nodal points, the intermediate portions [of a cord] which vibrate are termed bellies or ventral segments. 1831 M. Faraday Exper. Res. xlvi. 318 Neither sand nor filings could rest on the quiescent, or nodal, lines. 1845 Philos. Trans. (Royal Soc.) 135 360 Carbonic acid and nitrogen..might be bracketed with the metals which do not decompose water, as forming the nodal point or zero of the table. 1873 W. Lees Acoustics i. iii. 25 We have not only nodal points in a vibrating string, but we may have nodal lines in a vibrating plate. 1937 J. W. T. Spinks tr. G. Herzberg Atomic Spectra i. 41 On certain spherical surfaces about the nucleus, the ψ function is always zero. These are the nodal surfaces of the ψ function corresponding to the nodes of a vibrating string. 1990 A. Waterman Planetarium 75 Sandgrains on a plate stimulated to vibrate sweet notes from a violin gather to a pattern in the nodal lines. nodal point 3. figurative. Designating a centre of convergence or divergence; focal. Chiefly in nodal point. ΘΚΠ the mind > attention and judgement > attention > earnest attention, concentration > [noun] > focus of attention centre1582 focus1751 focal point1755 nodal point1862 centre stage1887 the world > space > relative position > inclination > state or quality of being convergent > [noun] > point of convergence confluity1623 cone1705 meeting-point1818 conflux1826 confluence1828 nodal point1862 meeting-place1897 node1902 node point1957 1862 M. Hopkins Hawaii 238 These nodal points [in history] determine the length of his chapters. 1863 J. D. Dana Man. Geol. 598 These species occupy nodal points, as they may be called, or points of divarication. 1895 T. Hardy Jude vi. ii He was their nodal point, their focus, their expression in a single term. 1915 J. Buchan Nelson's Hist. War IV. 127 Its main railway station, the nodal point of the Polish lines, lies in the suburb of Praga. 1964 T. McGrath Sel. Poems 3 At nodal points the personal love Changes, if it is pure enough, From single idol in man or woman To equal love for all that's human. 1993 Archit. Rev. Jan. 45/1 Meeting House Square is conceived as a nodal square on the converging axes of several new pedestrian routes through Temple Bar. 2001 Fortean Times Jan. 53/3 Like the tree circle, they are frequently found to be built on earth energy nodal points at the junction of dowsable leys. < as lemmas |
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