| 单词 | diopter |
| 释义 | diopter —dioptral, adj. /duy op"teuhr/, n. 1. Optics. a unit of measure of the refractive power of a lens, having the dimension of the reciprocal of length and a unit equal to the reciprocal of one meter. Abbr.: D 2. an instrument, invented by Hipparchus, to measure the apparent diameter of the sun or moon or to estimate the size or elevation of distant objects. Also, esp. Brit., dioptre. [1585-95; < L dioptra < Gk: instrument for measuring height or levels, equiv. to di- DI-3 + op- (for ópsesthai to see) + -tra n. suffix of means] |
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