Elements of astronomy: accompanied with numerous illustrations, a colored representation of the solar, stellar, and nebular spectra, and celestial charts of the northern and the southern hemisphere (1875)
Lockyer, Norman, Sir, 1836-1920 · New York, D. Appleton and company · leaf 238
Fig. 93.—Bi-convex Lens, causing Parallel Eats to converge to a Focus. kinds of lenses have we mainly to do? Name and descrihe them. 418. Howare two prisms arranged in Fig. 92 ? What is their effect on two parallel beams ?How may we regard a bi-convex lens ? What will be the action of such a lens…
Astronomy
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