Appleton's dictionary of machines, mechanics, engine-work, and engineering (1869)
New York, Appleton · leaf 225
r radii or distances are unequal. A plano-convex lens, Fig. 2582, is bounded by a plane surface on one side, and by a convex one onthe other. A double concave lens, Fig. 2583, is bounded by two concave spherical surfaces wdiose centres are onopposite sides of the lens. A plano-concave lens, Fig.… … The focal distance, or distance of the focus from the surface of the lens, depends both upon the formof the lens and of the refractive power of the substance of wdiich it is made ; in a glass lens, both sidesof which are equally convex, the focus is situated nearly at the centre of the sphere of…
Mechanical engineering
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