Elementary natural philosophy : designed for high schools and academies (1881)
Griffin, La Roy F. (La Roy Freese), 1844-1916 · Philadelphia : Sower, Potts & Co. · leaf 201
e number made is very great, and some ofthem are wonderfully beautiful. 676. Concave Mirrors are usually either sections of ahollow sphere or of a paraboloid. The former will showthe principle of all. 677. Focus. Rays of light reflected from concave mir-rors meet at some point called a Focus.… … Fig. 215Fig. 215 shows how the principal focus is determined, The parallel rays meet the mirror M at the points a, b, c, d, etc. Eadii
Physics
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