Sonara: Sonoluminescence
Optics, Waves & Sound arc, page 114 of 193. Back to The Pixelated Physics Universe
Who they are
Sonara traps a single bubble in sound, and on every squeeze it flashes.
Sonara is a character of the Optics, Waves & Sound arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
A gas bubble held in water by a strong sound wave swells and then collapses violently, giving off a flash of light lasting 60–250 picoseconds, once per sound cycle. The bubble's radius follows the Rayleigh–Plesset equation. Gaitan et al. first trapped a single sonoluminescing bubble in 1992; Gompf et al. (1997) measured flash widths from about 60 ps to over 250 ps.
$$ \begin{gathered} R\ddot{R} + \tfrac{3}{2}\dot{R}^{2} = \frac{1}{\rho}\left[p_g - P_0 - P(t) - \frac{4\mu\dot{R}}{R} - \frac{2\sigma}{R}\right] \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $R$ | bubble radius | m |
| $\dot{R}$ | bubble wall speed | m/s |
| $\ddot{R}$ | bubble wall acceleration | m/s² |
| $\rho$ | liquid density | kg/m³ |
| $p_g$ | gas pressure inside the bubble | Pa |
| $P_0$ | ambient pressure | Pa |
| $P(t)$ | acoustic driving pressure | Pa |
| $\mu$ | liquid viscosity | Pa·s |
| $\sigma$ | surface tension | N/m |
Honest caveat: How the light is made is still debated, and the bubble does not have a single agreed temperature.
Status: part of this topic is unsolved, unconfirmed or debated. The text above says which part; treat it as an open question, not settled fact.
Sources
- Gaitan, Crum, Church & Roy (1992) Sonoluminescence and bubble dynamics for a single, stable, cavitation bubble, J. Acoust. Soc. Am. 91, 3166
- Gompf et al. (1997) Resolving Sonoluminescence Pulse Width with Time-Correlated Single Photon Counting, Phys. Rev. Lett. 79, 1405
- Brenner, Hilgenfeldt & Lohse (2002) Single-bubble sonoluminescence, Rev. Mod. Phys. 74, 425
Crossovers
Sonara meets Levitah (Held by Sound). Levitah holds a bubble or droplet in a standing sound wave. Sonara does the same, then drives the bubble so hard that it collapses and flashes. How the light is made is still debated.
Sonara meets Chimella (Hot Chocolate Effect). Chimella's bubbles lower the speed of sound in hot chocolate. Sonara's single bubble collapses in a sound field. Sound and bubbles pull on each other in both mugs.
Wear the lore
- Sonara – Sonoluminescence Physics T-Shirt
- Related infographic poster: Rayleigh's Collapse – Plate 008 Physics Poster
Concept keywords: Sonoluminescence, Sonara, Optics, Waves & Sound, physics lore, Pixelated Physics