Issues in calibration. Primary reference standards. A reference standard for a unit of measurement is an artifact that embodies the quantity of interest in a way that ties its value to the reference base. At the highest level, a primary reference standard is assigned a value by direct comparison with the reference base.
Refraction of Sound. Refraction is the bending of waves when they enter a medium where their speed is different. Refraction is not so important a phenomenon with sound as it is with light where it is responsible for image formation by lenses, the eye, cameras, etc. But bending of sound waves does occur and is an interesting phenomena in sound.
Refraction (optics). Refraction is the phenomenon that causes a light ray to bend when it hits an optical lens surface (or other medium that can act to transmit light e.g. water). Refraction occurs when light strikes the surface of the new medium.As the light enters a dense medium is slows the light wave down.The light is passing from an optical medium (like air) to another optical medium (like glass).As the density of the medium changes the light striking the surface is refracted. The refraction is most obvious when when the light strikes the new medium at an angle.he light is passing from an optical medium (like air) to another optical medium (like glass). As the density of the medium changes the light striking the surface is refracted. The refraction is most obvious when when the light strikes the new medium at an angle.