Bubbles from sound

Published: Monday 28 February 1994

High-temperature gas bubbles that dance and emit light have been developed by the Indian Institute of Science (IISc), Bangalore, by passing ultrasound through water. These astounding light-emitting bubbles (LEBs) can eventually be applied for inducing ultrafast chemical reactions in liquids and initiating nuclear fusion.

The LEBs are generated from distilled water contained in a glass vessel that is in physical contact with a device generating ultrasound at a frequency matching the "natural vibration mode" of the water-filled vessel. When the power level of the ultrasound and its frequency are right, the bubble "dance and light show" begins, emitting pulses of blue light at the exact frequency of the driving ultrasound.

Says Vijay Arakeri, IISc scientist who has observed this phenomenon for the first time in India, "A gas bubble entering the vessel gets trapped at its centre and begins to oscillate, growing to 10 times its original size. It then collapses inward, and begins to emit light." The glow emitted by the bubble could be increased to "look like a star" by cooling the water and dissolving oxygen in it. Enlarging the bubble size could raise the temperature to the level needed for the study of thermo-nuclear fusion.

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