Planspeglar

Planspeglar is the Swedish term for plane mirrors, a type of optical mirror with a flat, highly polished reflective surface. When light rays strike a planspegel, the law of reflection applies: the angle of incidence equals the angle of reflection. A virtual image is produced behind the mirror at the same distance from the surface as the object is in front; the image is upright and the same size as the object, though it is laterally inverted.

Key properties include the absence of magnification and minimal distortion when the surface is truly flat. Image quality depends on surface flatness, coating quality, cleanliness, and the wavelength of light. Plane mirrors do not alter angular magnification, unlike curved mirrors, and they preserve the orientation and scale of the viewed scene.

Construction typically involves a glass or other substrate with a reflective coating applied to one side, such as aluminum or silver, often protected by a durable overcoat. High-quality plane mirrors used in scientific and technical applications may undergo precision polishing and metrological checks to ensure flatness and surface quality.

Applications span everyday and professional domains. Household mirrors are the most common example, but planspeglar are also essential in optical experiments, laser systems, periscopes, measurement setups, and other instruments where a non-magnifying, undistorted reflection is required.

Historically, the principles of reflection have been studied since ancient times, with plane mirrors becoming widespread tools in both daily life and science as optical theory matured. See also: Mirror, Periscope, Optical bench.