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
Optic axis of a crystal displays. Optic axis of a crystal An optic axis of a crystal is a direction in which a ray of transmitted light suffers no birefringence (double refraction). An optical axis is a direction rather than a single line: all rays that are parallel to that direction exhibit the same lack of birefringence. Crystals may have a single optic axis, in which case they are "uniaxial", or two different optic axes, in which case they are "biaxial". Non-crystalline materials generally have no birefringence and thus, no optic axis. A uniaxial crystal (e.g. calcite, quartz) is isotropic within the plane orthogonal to