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-135 anti-ballistic missile system A-135 anti-ballistic missile system The A-135 (NATO: ABM-3 Gorgon) anti-ballistic missile system is a Russian military complex deployed around Moscow to counter enemy missiles targeting the city or its surrounding areas. It became operational during 1995. It is a successor to the previous A-35, and complies with the 1972 Anti-Ballistic Missile Treaty. The A-135 system attained "alert" (operational) status on February 17, 1995. It is operational although its 51T6 (NATO reporting name: SH-11) component was deactivated in February 2007. A newer missile (PRS-1M) is expected to replace it. There is an operational test version of the system at the test