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
h the rays were emitted from the point L\ this point being called the virtual focus. 2,688 HAWKINS ELECTRICITY when the former rays emerge, they move farther from the axisthan the latter, and form a diverging pencil HK, GM. These rayscannot produce a real focus, but their prolongations intersect in… … 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{
Electrical engineering
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