refraction [ri`frak·shǝn] ELECTROMAGNETISM The change in direction of lines of force of an electric or magnetic field at a boundary between media with different permittivities or permeabilities. PHYSICS The change of direction of propagation of any wave, such as an electromagnetic or sound wave, when it passes from one medium to another in which the wave velocity is different, or when there is a spatial variation in a medium's wave velocity. |