“If an underwater bubble is collapsed by loud sound, light is produced and no one knows why” says one of those click-bait social media posts with no citation—“light produced” and “no one knows why.” Is either true?
Not something I heard during my studies of underwater acoustics—but then, we weren’t very concerned with light.
There exist models describing sonoluminescence example
Single bubble sonoluminescence is not an exotic phenomenon but can quantitatively be accounted for by applying a few well-known, simple concepts: the Rayleigh–Plesset dynamics of the bubble’s radius, polytropic uniform heating of the gas inside the bubble during collapse, the dissociation of molecular gases, and thermal radiation of the remaining hot noble gas, where its finite opacity (transparency for its own radiation) is essential. A system of equations based on these ingredients correctly describes the widths, shapes, intensities, and spectra of the emitted light pulses, all as a function of the experimentally adjustable parameters, namely, driving pressure, driving frequency, water temperature, and the concentration and type of the dissolved gas. The theory predicts that the pulse width of strongly forced xenon bubbles should show a wavelength dependence, in contrast to argon bubbles.
This is an example of the so-called Mandelstam-Brillouin scattering, which is a close relative of the Raman effect. (In fact, Mandelstam and Landsberg possibly discovered the Raman effect even before Raman, but were late to publish.)
