Diffraction of light by ultra-sonic waves of very high frequencies

Abstract

Using a specially constructed rectifier giving 1,100 volts and a Taylor T 55 valve with amphenol bases and special inductances, frequencies up to 100 megacycles per second have been produced. A tourmaline plate prepared in this laboratory with a thickness of 2 mm. and a fundamental of about 2 Mc./sec. is made to oscillate up to its 54th harmonic, and at all stages it could be employed to maintain stationary waves in a column of water in the usual manner. Diffraction patterns at almost all the frequencies in the range 2 to 100 Mc./sec. could be observed. The highest frequency so far adopted1 for such work is only 52.5 Mc./sec. In order to detect dispersion, if any, of ultra-sonic velocity in water, the crystal has been simultaneously excited by us at two frequencies and both patterns photographed on the same plate at the same instant.