Elementary natural philosophy : designed for high schools and academies (1881)
Griffin, La Roy F. (La Roy Freese), 1844-1916 · Philadelphia : Sower, Potts & Co. · leaf 120
-duced by the body A to thatFig-136. produced by the body B at the points x, y, z, etc., where the circles become tangent, and atthe points a, b, c, etc., where the circles cross. Half way betweenthese points, on the line AB, is a point of rarefaction, and fromthe same cause, this will be rendered… … *Its accurate demonstration belongs to Optics. BEATS AND ECHOES. Ill the source A , and one of rarefaction from B, come together. Themotion of the molecules of air is now the difference of the two, ornothing. An ear then placed at such points will hear no sound. 387. Reflection frequently produces…
Physics
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