Natural philosophy, for the use of schools and academies (1883)
Author: Gillet, J. A. (Joseph Anthony), 1837-1908; Rolfe, W. J. (William James), 1827-1910
Fundamental and Harmonic Vibrations.
Strew sand upon a horizontal plate of brass, and then, holding it with the thumb and finger, draw a bow across the edge of the plate so as to throw it into vibration. The sand will be tossed up and down, and first, but will quickly come to rest in definite lines, called nodal lines.
These are lines of rest which separate the vibrating segments of the plate. By touching the plates at different points with the thumb and finger, a great variety of figures may be produced with the sand, showing that it is possible for the plate to break up into vibrating segments in a great many different ways. A series of these nodal figures is shown in fig. 125