Natural philosophy. being a hand-book of chemical physics, or, The physics of heat, light and electricity (1869)
Sangster, John Herbert, 1831-1904 · Montreal : J. Lovell · leaf 137
umber of lens through which the light has to pass before reachingthe eye, a; = the amount of light transmitted by each lens, commonly aboutT^iT, F;= visual power, P = penetrating power, /= illuminating power,and M= magnifying power. Th .r_ foc^^6°gth of object-glass D* oc focal length of eye-glass… … It consists essentially of a dark chamber, or tin box, A A, which containsthe source of Ulumination, the lenses, &c. The parabolic reflector p q,receives the diverging rays of light from the lamp, L, and reflects themparallel upon the convex illuminating lens, m. The lens m concentrates…
Physics
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