Sonoluminescence. Single-bubble sonoluminescence - A single, cavitating bubble.
Video of synthetic wound cavity collapsing creating sonoluminescence. Long exposure image of multi-bubble sonoluminescence created by a high-intensity ultrasonic horn immersed in a beaker of liquid. Luminescence (physics. Luminescence. Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation.
It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a substance as a result of heating. Historically, radioactivity was thought of as a form of "radio-luminescence", although it is today considered to be separate since it involves more than electromagnetic radiation.