Moulton, Forest Ray, 1872-1952 · New York, The Macmillan company · leaf 417
the echelon, gives high dispersion without great loss oflight. Only the first type, which is most used in astronomy,will be more fully described here. The basis of the prism spectroscope is the refraction andthe dispersion of light when it passes through a prism. LetL, Fig. 138, represent a beam of… … 370 AN INTRODUCTION TO ASTRONOMY [ch. xi, 222 medium, it is bent from the perpendicular to the surface.This change in the direction of the beam of Hght is itsrefraction. Not only is the beam of light refracted, but it is also spreadout into its colors. As it enters the prism the violet lightis…
Astronomy
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