The outlines of physics: an elementary text-book (1897)
Nichols, E. L. (Edward Leamington), 1854-1937 · New York, The Macmillan Company; London, Macmillan & Co., Ltd. · leaf 407
lens, reach-ing finally a point I. This is called the principal focusof the lens. If, in the same way, a source of light at / bemoved off to an infinite distance, its rays will come to afocus at F (Fig. 365). The distance from the lens to theprincipal focus is called the focal length of the lens.… … Fig. 365. point we have an object on one side of the lens, as inFig. 366, light from all points of the object will be broughtto a focus at the corresponding point behind the lens, andthe result will be an image. This image, like the image
Physics
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