Elementary astronomy; a beginner's text-book (1899)
Holden, Edward Singleton, 1846-1914 · New York, H. Holt and company · leaf 464
ced parallel to the edge A of theprism, the purest spectrum is obtained. The different spectra do notoverlap. Fraunhofer tried this experiment in 1804, and hefound that the spectrum of the Sun was interrupted by cer-tain dark lines, fixed in relative position. These are theFraunhofer lines, so… … Fig. 221.—The Spectroscope. cular hole is used, and they belong to the incident lightand are not produced by the apparatus. This simply ren-ders them visible. They are not seen when the light comesthrough wide apertures, on account of the overlapping ofthe various images. (See Fig. 222.) The…
Astronomy
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