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.
Noun. 1. refraction-the change in direction of a propagating wave (light or sound) when passing from one medium to another. physical phenomenon-a natural phenomenon involving the physical properties of matter and energy. birefringence, double refraction-splitting a ray into two parallel rays polarized perpendicularly.