Introductory course of natural philosophy for the use of schools and academies. Ed. from Ganot's popular physics. By William G. Peck (1869)
Ganot, Adolphe, 1804-1887, Peck, William Guy, 1820-1892 · New York A.S. Barnes · leaf 280
8.) What is a F<x3us ? The Principal Focus? Illustrate MIRRORS. 277 Fig. 163 shows the manner 01 determining the principal focus byexperiment, making use of a beam of light coming from the sun.In this form the concave reflector may be used to collect the rays forth« purpose of developing a great… … Fig. 164. different from F Thus, in Fig. T64, the pencil of rays,coming from the point B, are brought to a focus at b, be-tween F and C. Had the rays emanated from b, theywould have been brought to a focus at B. These pointsare so related as to receive the name of conjugate foci.Hence we have the…
Physics
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