Hawkins electrical guide ... : questions, answers & illustrations : a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications ; a practical treatise (1914)
Hawkins, N. (Nehemiah), 1833-1928 · New York : T. Audel & Co. · leaf 34
L^S^ FiG. 3,790.—Virtual focus in double convex lens. In the figure, L is the position of the luminoussource between the principal focus and the lens; F is the principal focus, and L, the virtualfocus corresponding to the position L of the luminous source. C-t{ … Fig. 3,791.—Foci of convex mirrors. This type of mirror has only virtual foci. Let SI, and TKbe rays parallel to the principal axis of a convex mirror. These rays, after reflection, takethe diverging directions IM, KH, which, when continued, meet at a point F, which is theprincipal virtual focus.…
Electrical engineering
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