Sonoluminescence
- nicolelyu812
- Mar 30, 2024
- 2 min read
Updated: Mar 31, 2024
When a mantis shrimp snaps its claws, it sends a high speed water jet through the ocean, creating a sonic shock wave (“snap!”) and surprisingly, light. Huh?? This phenomenon is an example of sonoluminescence, the emission of light from a small gas bubble in liquid under sound of the right frequency. Although the light flashes last for so little (only ~100 picoseconds, 10 billionths of a second), the temperature is astonishing - up to 50000 Kelvins (nearly 10 times hotter than the sun’s surface)! What's up with the heat and the flash?
The process
Under low pressure within the sound wave, water is “pulled apart” to form a void of bubble vapour, thus creating a bubble.
Sound waves are made up of high pressure regions (compressions) and low pressure regions (rarefactions). When a compression meets the bubble, the bubble collapses under the high pressure. When a rarefaction meets the bubble, the bubble expands due to lower pressure. This rapid expanding and collapsing is known as cavitation.
When collapsing, heat energy is released by the pressure increase (known as adiabatic heating). Latent heat energy might also be released through condensation of water vapour back to its liquid form.
What about the flash?
The flash is still not fully understood, unfortunately😢. However, there are several proposals of how the the “flash” is created from the heat.
Firstly, it might be that the noble gas present in the bubble (as it could dissolve in seawater) glowed under high temperatures. Another option is that the heat caused water vapour to ionize to H+ and OH- ions, giving off light upon recombination.
Or it could be about electrons. Electrons might be rapidly accelerated during these processes, creating changing electric and magnetic fields thus emitting electromagnetic radiation as light. Or maybe the electrons had enough energy to break free from the molecules, creating plasma in the bubble which emits light. We still want to know.
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