Elements of natural philosophy (Volume 2-3) . t, after it was at A B. Any molecule situatedat the intersection of the smaller circles will obviouslybe agitated by the waves transmitted to it from mole-Eesultantcules at their respective centres ; and the resultant clis- ^placement ofplacement will, §55, §56, be the algebraic sum of tlieapaltlc1displacements due to each when superposed. Hence, to find the disturbing effect of any wave upona given molecule at a given time, divide the wave intoa number of small parts, consider each part as a centreof disturbance, and find by summation the aggregat
Elements of natural philosophy (Volume 2-3) . t, after it was at A B. Any molecule situatedat the intersection of the smaller circles will obviouslybe agitated by the waves transmitted to it from mole-Eesultantcules at their respective centres ; and the resultant clis- ^placement ofplacement will, §55, §56, be the algebraic sum of tlieapaltlc1displacements due to each when superposed. Hence, to find the disturbing effect of any wave upona given molecule at a given time, divide the wave intoa number of small parts, consider each part as a centreof disturbance, and find by summation the aggregate ofall the disturbances of the given molecule by the wavescoming from all the points of the great wave. The cause which makes the disturbance of a singlemolecule at one instant the occasion of the simultaneousdisturbance of an indefinite number of surrounding mole- , . Principle of new cules at a subsequent instant, is called the principle of divergencenew divergence, of which frequent use will be made instated>the subject of p 2\£ rrrmsii § 64. Let us trace the consequences of this principle Its application toin its application to the passage of sound through aper- B0U^d ^ghtures and around the edges apertures and Of Objects. Take a parti- F1* *? around corner*; tion MW, through which there is an opening A B, and suppose a spherical wave of sound to proceed from a centre G Only that portion of the wave which comes against the opening can pass through, and the wave front on the opposite side of the jmrtition will be found by taking the diffe-Illustration; rent points of the segment A B, within the opening as centres, and radii equal to V. t, and describing a series of elementary arcs, and drawing a curve tangent to them
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