Lawrence A. Crum
Sean Cordry
Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105
In 1896, Henri Becquerel discovered that a uranium salt could darken a photographic plate, and from this effect went on to discover radioactivity. In 1934, Frenzel and Schultes discovered that acoustic waves, generated in a water bath, could also darken a photographic plate. They attributed this effect to luminescence from the sound field, a phenomenon that would later be known as sonoluminescence. A sound field by itself does not cause luminescence; it is through the mechanism of acoustic cavitation, whereby microscopic gas bubbles are caused to oscillate so violently that a remarkable energy concentration occurs. Under certain conditions, the cavitation event is transitory, and self-destructs within a few acoustic cycles; under other conditions, a stable bubble will luminesce for extended periods of time. This initial presentation will serve as a general review of the phenomenon of acoustic cavitation and demonstrate how bubble dynamics leads to many of the observed effects. Later papers in this session will provide more detail of various aspects of the general phenomenon. [Work supported in part by the Office of Naval Research.]