The geography of the heavens, and class-book of astronomy: accompanied by a celestial atlas (1873)
Burritt, Elijah H. (Elijah Hinsdale), 1794-1838, Mattison, Hiram, 1811-1868, ed, Whitall, Henry, 1819-1887? Celestial planisphere · New York, Sheldon & company · leaf 318
half its refractingpower is gone, so that the raysare not so soon refracted to afocus. In this case, the focal dis-tance is equal to the diameter ofthe sphere formed by extendingthe convex surface of the lens;while with the double-convex lens,the focal distance is only equal to the radius of such… … a focus atthe circle RAYS DISPERSED BT REFRACTION. cace lens disperses pa-rallel rays, as if theydiverged from the cen-ter of a circle formedby the convex surfaceproduced. In this cut, the parallel raysA are dispersed by the double-concave lens C, as shown atB; and their direction, asthus…
Constellations · Stars
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