Elementary natural philosophy : designed for high schools and academies (1881)
Griffin, La Roy F. (La Roy Freese), 1844-1916 · Philadelphia : Sower, Potts & Co. · leaf 212
focus is moved further away. Thus if the lightbe placed at L, thefocus will be at 1.These points are con-| jugate foci, for eachis the focus of a lightplaced at the other. Fig. 232. The foci of con- vex lenses are real, for if a screen be placed at these points,it is brightly illuminated. The light… … IMAGES BY CONVEX LENSES. 203 II. When the Object is nearer the Lens than the PrincipalFocus. When it is at the Principal Focus, the rays becomeparallel, and no image is formed. 707.1. Image of an Object beyond the Principal Focus. The image is determined by finding two points, the extrem-ities, as…
Physics
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