sono = sound, luminescence = light, Sonoluminescence = light caused by sound.
you take a flask of water, put speakers on the sides of the flask, and
turn the volume way up, something interesting can happen. Little
bubbles will form. The sound waves push and pull the water so much that
the water actually pulls apart. A little bit of vacuum is left behind.
that is dissolved in the water then begins to fill the vacuum. Water
evaporates into the vacuum. When the bubble tries to collapse, it is
now filled with gas. The sound wave that is powerful enough to pull the
water apart, also pushes the gas bubble closed with a lot of strength.
a brief fraction of a second, the gas is compressed so much that it
heats up until it glows. What we see is a little flash of light. That
light flashes with each wave of sound that hits the bubble. It looks
like a continuous spark of light in the middle of the water. Even
though the equipment can be bought for a few hundred dollars, getting
everything perfect so that it works is difficult. You need a very
spherical flask, ultrasonic speakers around the outside surface of the
flask and electronics to drive the speakers. Experimenters also put
different gasses in the water to see what happens.
(republished on 07/28/06)