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.. the change of direction of a ray of light, sound, heat, or the like, in passing obliquely from one medium into another in which its wave velocity is different. 2. a. the ability of the eye to refract light that enters it so as to form an image on the retina. b. the determining of the refractive condition of the eye.