refraction /rifrak″shən/ [L, refringere, to break apart] , 1. n., the change of direction of energy as it passes from one medium to another of different density. 2. n., an examination to determine and correct refractive errors of the eye. 3. n., (in ultrasonography) the phenomenon of bending wave fronts as the acoustic energy propagates from the medium of one acoustic velocity to a second medium of differing acoustic velocity. 4. adj., pertaining to the recovery period after an action potential either in muscular or nervous tissue. −refractive, adj.
