. The Bell System technical journal . As before P stands for the source of the primary waves, Q for thepoint (on the wall of our imaginary bulb) where the scattered wavesare to be measured. The question is: under what condition do thescattered waves from A and B and C all three reinforce one anotherbest at (2? under what condition do the waves from all three groupsarrive at Q in identical phase? 9 Q 9 9 9 9 9. 9 9 9 Fig. 5—Illustrating diffraction by a plane of atom-groups in regular array. Evidently we have only to restate the condition that the wavesfrom A and B arrive in identical phase, an
. The Bell System technical journal . As before P stands for the source of the primary waves, Q for thepoint (on the wall of our imaginary bulb) where the scattered wavesare to be measured. The question is: under what condition do thescattered waves from A and B and C all three reinforce one anotherbest at (2? under what condition do the waves from all three groupsarrive at Q in identical phase? 9 Q 9 9 9 9 9. 9 9 9 Fig. 5—Illustrating diffraction by a plane of atom-groups in regular array. Evidently we have only to restate the condition that the wavesfrom A and B arrive in identical phase, and supplement it with oneexactly like it for the waves from A and C. We have only to repeatequation (3), and beside it write another like it in which a is replacedby a, the distance from ^ to C; 0 by <^, the angle between thedirection of the primary waves PA and that from A to C\ and 6 by 6,the angle between the direction of the scattered waves AQ and thatfrom A to C. When the waves from all three atom-groups reinforceone another, both equations prevail: a(cos d — cos 0) = wX,a(cos 6 — cos ) = n\. (3)(4) ^ The choice of groups to serve as B and C is purely a question of same results are reached whichever two we choose, so long as they are notcollinear with A ; but the results when reached are in a form which depends uponthe choice, and is most convenient when AB and AC a
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
