Sonoluminescence

A bubble trapped by ultrasound oscillates, collapses violently, and emits a picosecond flash of light — the interior reaches temperatures hotter than the Sun's surface.

Radius: - μm Velocity: - m/s Pressure: - atm Temp: - K Flashes: 0
The Rayleigh-Plesset equation governs bubble dynamics: R·R̈ + (3/2)Ṙ² = (1/ρ)[P_gas − P_∞ − P_drive]. At minimum radius, adiabatic compression heats the gas to ~50,000 K (some estimates higher), causing plasma formation and UV/visible light emission over ~100 ps. Single-bubble sonoluminescence was first demonstrated by Gaitan & Crum in 1989.