Modes of Vibration of a Round Plate Cut from a Quartz Crystal

Abstract

A large number of modes of vibration of a round quartz crystal plate of the “Curie” cut were photographed by means of the ionized gas appearing at the antinodal regions when the plate was mounted in an atmosphere of neon or argon at a few mm pressure and thrown into vibration piezo-electrically by a radio frequency oscillator.Two general types of vibration of the plate were found. In the first kind the plate was symmetrically divided up into nodal and anti-nodal regions forming patterns peculiar to the exciting frequencies. In the second kind of which less evidence was found the vibration consisted of standing waves along chords or diameters of the plate with reflection at the edges. The crystal rested on a round brass plate which served as the lower electrode. Two different top electrodes were used, a point and a screen, the same pattern being photographed with each for the more prominent modes of vibration and from this it was concluded that the patterns were independent of the electrode arrangement. Evidence of vibration along axes oblique to the surfaces of the crystal plate was found. All vibrations observed were believed to be compressional in nature.