In'çi-dençe, n.
n. [Fr. incidence, Sp. incidencia, It. incidenza, L. Lat. incidentia. See infra.]
Sense 1. A falling on or occurring; an accident or casualty. Shak.
Sense 2. (Physics.) The direction in which a body, or a ray of light or heat, falls on any surface.
In equal incidences there is a considerable inequality of refractions. Newton.
A, B, H, angle of incidence; C, B, H, angle of reflection.
Angle of incidence, the angle which a ray of light, or the line of incidence of a body, falling on any surface, makes with a perpendicular to that surface; also formerly the complement of this angle.—Line of incidence, the line in the direction of which a surface is struck by a body, ray of light, and the like.
