The deflection of light waves when passing through narrow slits to form fringes of partial light and dark bands.
The change occurring in light when it passes through crystals, prisms, or parallel bars in a grating, in which the rays are deflected and thus appear to be turned aside. This produces dark or colored bands or lines. The term is also applied to similar phenomena in sound.
The alteration in the path of light as it transitions from one medium to another, causing it to bend. For instance, a straight stick partially submerged in water appears to bend at the point where it enters the liquid.