Philosophical instructor, or, Webster's elements of natural philosophy : subdivided into principles and illustrations ; intended for academies, medical schools, and the popular class-room (1824)
Eaton, Amos, 1776-1842, Webster, John, fl. 1804-1824 · Albany : Printed by Websters and Skinners ... · leaf 170
LENSES. 16*7 … the rarer medium of the air, still converges to a pointsomewhere in the axis ; therefore, if both sides of thelens be spherical, the convergency will still be great-er, and the rays will meet in some point nearer to thecentre of the lens. Consequently, if a b bea double convex lens, theparallel…
Physics
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