thumb|image of an explosion with a labeled shock wave
Atmospheric focusing is a type of wave interaction causing shock waves to affect areas at a greater distance than otherwise expected. Variations in the atmosphere create distortions in the wavefront by refracting a segment, allowing it to converge at certain points and constructively interfere. In the case of destructive shock waves, this may result in areas of damage far beyond the theoretical extent of its blast effect. Examples of this are seen during supersonic booms, large extraterrestrial impacts from objects like meteors, and nuclear explosions.
Density variations in the atmosphere (e.g. due to temperature variations), or airspeed variations cause refraction along the shock wave, allowing the uniform wavefront to separate and eventually interfere, dispersing the wave at some points and focusing it at others. When objects like planes travel faster than the speed of sound, they create sonic booms and pressure waves that can be focused. As the meteor enters Earth’s atmosphere and reaches lower altitudes, it can create a shock wave.
See also
- Knudsen number
- Nuclear weapons testing
- Rankine–Hugoniot conditions