Luminescence Produced as a Result of Intense Ultrasonic Waves

Abstract

The luminescence produced by intense ultrasonic waves has been investigated in a number of water solutions and organic liquids in the frequency range 0.66—2.0 mc/sec. Together with direct visual tests, quantitative measurements have been performed for which a photometric method has been developed. The results show that luminescence, when it does occur, is always present with cavitation and starts at the same sound intensity as cavitation. A quantitative relationship is established between intensity of luminescence and chemical yield induced by ultrasonics. From this it is concluded that, at least in some of these cases, the phenomenon is chemiluminescence. None of the organic liquids tested showed any luminescence except for nitrobenzene in which the luminescence was very weak in the frequency range and under the physical conditions examined. It is not possible at present to conclude whether this weak luminescence is due to some chemical reaction occurring in it or to a different process. An apparent frequency dependence for the intensity of luminescence was observed; however, it is shown that the threshold of cavitation is the frequency‐dependent phenomenon.