Elementary natural philosophy : designed for high schools and academies (1881)
Griffin, La Roy F. (La Roy Freese), 1844-1916 · Philadelphia : Sower, Potts & Co. · leaf 197
ntre appearslight on a dark background if the stronger light is infront of it, and dark on a light background if the moreintense light is beyond. It is then moved until the spotdisappears, when both sides are equally illuminated. Thecomparative distance of the two lights determines the in-tensity,…
Physics
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