Lecture Notes on Mechanics, Sound and Light (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1890 Excerpt: ...motions due to the two systems for equal successive time intervals; and since the same material point is subject to the two motions, it must be on successive intersections of these parallel lines at the ends of successive equal intervals. Any successive pair of intersections traversed will lie at the diagonally opposite corners of the small rectangles made by the parallel lines. A curve traced through the points will represent the resulting motion. Thus in Fig. 38 the periods are as 2 to 3 and the circles are divided into 8 and 12 parts respectively. The curve repre sents the case of no difference in phase. The results obtained analytically are confirmed by Blackburn's pendulum and Lissajou's forks. PHENOMENA OF REFLECTION. 113. The Principle Of Huyghens. (D., 106; A. & B., 356.) Let a, Fig. 39, be a center or source of spherical sound waves. The principle of Huyghens is that every point of the wave-surface m n becomes a new center of disturbance from which waves of sound are propagated in the same manner as from the original center. This follows from the consideration that every particle on the wave-surface has the same vibratory motion, except in respect to amplitude, as the first particle disturbed, and therefore stands in the same relation to adjacent particles and communicates motion to them in the same manner. It therefore becomes Figubh 39. itself a center of disturbance. Let the points of the surface m n be such centers from which waves proceed for a short distance c d. The number of such waves being indefinitely large, they will ultimately coalesce to form the new wave-surface m' n' which is tangent to all the elementary wave-surfaces. 114. Reflection Of A Plane Wave At A Plane Surface (D., 112.) Let A B, Fig. 40, be a portion of the plane adva...