- minimum angle of deviation
The smallest angle through which light is bent by an optical element or system. In a prism, the angle of deviation is a minimum if the incident and exiting rays form equal angles with the prism faces. The angle is important relative to prism spectroscopes because it can be easily determined. For a prism, the minimum angle of deviation is dependent upon the material of the prism, the apex and cut angles of the prism, the angle of incidence the light ray strikes the prism, and the wavelength of light being used.