| Abstract
| - The application of high intensity ultrasound to liquids leads to cavitation. In contrast to the homogeneoussituation this is poorly understood close to a surface despite the implications for many biological, chemical,and physical applications. By using ultrafast electrochemical equipment and arrays of electrodes, we provethat the acoustic bubbles in the range of power ultrasound are hemispherical, not spherical as usually supposed,possessing a large range of possible diameters and oscillating at harmonics and sub-harmonics of the drivingfrequency (20 kHz). Most importantly, contrary to inferences made previously at much lower frequencies, noliquid microjet inside the bubble is observed.
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