Einfallswinkels

Einfallswinkels is the plural form of the German term Einfallswinkel, which in optics refers to the angle of incidence. It denotes the angle between an incident light ray and the normal to the boundary of a surface at the point where the ray meets that surface. In many texts the singular Einfallswinkel is used, but the plural Einfallswinkels appears when discussing multiple incidence angles across different interfaces or experiments.

The Einfallswinkel is defined relative to the normal line, which is drawn perpendicular to the surface at the point of contact. Its magnitude is typically measured in degrees, with 0° corresponding to light hitting the surface head-on and 90° corresponding to grazing incidence. The term is used across various contexts, including air–glass interfaces, water surfaces, and semi-transparent materials.

In the context of reflection, the law of reflection states that the angle of incidence equals the angle of reflection, so the Einfallswinkel and the reflected angle are equal with respect to the normal. In refraction, Snell's law relates the Einfallswinkel to the angle of refraction through the refractive indices of the two media: n1 sin(theta_i) = n2 sin(theta_t). This relation governs how light bends when crossing boundaries.

Measuring and applying Einfallswinkels involves instruments such as goniometers or optical benches to align the incident ray with the surface normal. Applications span from the design of anti-reflective coatings and optical lenses to solar energy systems and astronomical instrumentation.

See also: Einfallswinkel, Snell's law, reflection, refraction.