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 Waves. The speed of a wave depends on the elastic and inertia properties of the medium through which it travels. When a wave encounters different medium where the wave speed is different, the wave will change directions.
refraction definition. A change of direction that light undergoes when it enters a medium with a different density from the one through which it has been traveling â for example, when, after moving through air, it passes through a prism. (Compare reflection.) Note: Lenses and other optical instruments work through refraction of light.