Ausfallswinkel

Ausfallswinkel is a term used in optics to describe the angle at which a ray leaves a surface, measured relative to the surface normal at the point of incidence. It is the counterpart to the Einfallswinkel (angle of incidence), which is the angle of the incoming ray with respect to the same normal. Both angles are typically expressed in degrees.

In ideal, smooth surfaces the law of reflection states that the Ausfallswinkel equals the Einfallswinkel. This equal-angle relationship is the basis for many optical devices such as mirrors and periscopes. On rough, matte surfaces, reflection becomes diffuse: reflected rays emerge with a range of Ausfallswinkel directions rather than a single angle, reducing specular reflection.

The term is mainly used in geometrical optics, optical engineering, and related fields. It is also relevant in applications involving glare control, laser incidence on surfaces, and the alignment of optical elements. In practice, the Ausfallswinkel is determined using optical benches, goniometers, or angular measurement instruments to predict and control the path of reflected light.

Related concepts include Einfallswinkel (angle of incidence), Reflexion (reflection), and Snell’s law (refraction), which describes how rays bend when entering a different medium. While Ausfallswinkel focuses on the direction after interaction with the surface, refraction concerns the change in direction due to a change in medium.

See also: Einfallswinkel, Reflektion, Snell’s law.