Refraction (sound) a downward bending of the sound rays towards the ground. The same holds if the temperature is decreasing with height. If the temperature is increasing with height (inversion) and the wind speed is low, sound rays are bend upwards. Refraction (sound) Refraction, in acoustics, comparable to the refraction of electromagnetic radiation, is the bending of sound propagation trajectories (rays) in inhomogeneous elastic media (gases, liquids, and solids) in which the wave velocity is a function of spatial coordinates. Bending of acoustic rays in layered inhomogeneous media occurs towards a layer with a smaller sound velocity. This effect is responsible for
A-235 anti-ballistic missile system eliminates the use within the limited armed conflict and other situations of this kind; secondly, the system must be mobile, without a rigid binding to any object or center; thirdly, it must provide interception at an altitude of at least 500–750 km, that is, at Low Earth Orbit] . A-235 anti-ballistic missile system A-235 PL-19 "Nudol" () is a Russian anti-ballistic missile and anti-satellite weapon system in development. This system is designed to deflect a nuclear attack on Moscow and important industrial regions. The main developer of the system is JSC Concern VKO Almaz-Antey. The new system should replace the