innfallende

Innfallende is an adjective used in several Germanic languages, notably Norwegian and Danish, meaning incoming or incident. In scientific contexts it describes something that approaches or strikes a boundary from the exterior, as opposed to something that remains inside or exits.

In optics, innfallende Strahlen are rays that strike a surface. They form the angle of incidence with the surface normal. The concept is central to reflection and refraction: the angle of incidence relates to the angle of reflection, and Snell's law governs the refraction of innfallende light when entering another medium.

In daylighting and solar engineering, innfallende solar radiation describes sunlight reaching a surface and is used to assess illumination, heat gain, and energy performance of buildings. The term helps distinguish incoming radiation from transmitted or emitted radiation in architectural and environmental analyses.

Etymology: innfallende is formed from in- (toward) and fall (to fall) with the present-participle suffix -ende, yielding “falling inward” or “incoming.” Variants exist in related languages.

See also: incident ray, angle of incidence, reflection, refraction, Snell's law, daylighting, solar radiation.