ETYM Cf. French diffraction.
The bending of a wave around objects placed in its path.
When light passes sharp edges or goes through narrow slits the rays are deflected and produce fringes of light and dark bands.
The slight spreading of a light beam into a pattern of light and dark bands when it passes through a narrow slit or past the edge of an obstruction. A diffraction grating is a plate of glass or metal ruled with close, equidistant parallel lines used for separating a wave train such as a beam of incident light into its component frequencies (white light results in a spectrum).
The regular spacing of atoms in crystals are used to diffract X-rays, and in this way the structure of many substances has been elucidated, including recently that of proteins (see X-ray diffraction). Sound waves can also be diffracted by a suitable array of solid objects. + prikaži više

ETYM French réfraction.
The bending of a wave of light, heat, or sound when it passes from one medium to another. Refraction occurs because waves travel at different velocities in different media.
The change in direction of a propagating wave (light or sound) when passing from one medium to another.