Elementary natural philosophy : designed for high schools and academies (1881)
Griffin, La Roy F. (La Roy Freese), 1844-1916 · Philadelphia : Sower, Potts & Co. · leaf 194
aque. In this case, the Umbra is determined by drawing lines tangent to bothbodies. It is thefrustum of a conewhose apex is at thepoint P, Fig. 205,where the tangentsFig. 205. meet, beyond the luminous body. A section made as in case I, is a circle.Tangents can also be drawn which cross between the… … *This and all the views of shadows are shown in plane section. LAWS OF INTENSITY. 185 Diameter. This is a purely hypothetical case, and is deter-mined like case second. The Umbra is a cylinder.
Physics
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