Well's natural philosophy : for the use of schools, academies and privte students, introducing the latest results of scientific discovery and research ; arranged with special reference to the practical application of physical science to the arts and the experiences of everyday life ; with three hundred and seventy-five engravings (1873)
Wells, David A · New York : Ivison, Blakeman, Taylor and Co. · leaf 316
ages reflect-ed from a con-cave mirrorappear invert-ed, and whenerect f REFLECTION OF LIGHT. 311 from burning incense were caused to ascend at this point, an image would beformed upon it, and appear suspended in the air in an apparently supernaturalmanner. In this way, terrifying apparitions of… … The principal focus of a convex mirror liesas far behind the reflecting surface as in con-cave mirrors it lies before it. (See § 664.)The focus in this case is called the virtual focus, becauseit is only an imaginary point, toward which the rays ofreflection appear to be directed. Thus, let a b c d…
Physics · Science · Technology
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