Spejle

Spejle is the Danish word for mirrors, referring to reflective surfaces that form images by reflecting light. The term is used in Danish-language contexts to describe everyday household mirrors as well as specialized optical devices, and it is the plural form of spejl.

In optics, a mirror is a smooth, highly reflective surface that follows the law of reflection: the angle of incidence equals the angle of reflection. A plane spejl produces a virtual image that is the same size as the object and laterally inverted. The image appears as if located behind the mirror at the same distance as the object is in front of it.

Curved spejle, including concave and convex types, alter image properties. A concave spejl can form real images when the object is beyond its focal point and virtual, enlarged images when within the focal length. A convex spejl always forms virtual, diminished images and is widely used for safety and wide-angle viewing.

Manufacture and materials: modern mirrors are typically made from glass with a reflective coating on the back. Common coatings include silver or aluminum, often protected by additional layers to prevent corrosion. Some high-quality mirrors use dielectric coatings to maximize reflectivity and durability.

Applications: mirrors serve many purposes, including personal grooming, interior design and architecture, optical instruments, photography and film, vehicle and road safety, and various scientific experiments.

See also: mirror, reflective coating, curved mirror.