Licht

Licht is the Dutch term for light. In physics and everyday language, light refers to electromagnetic radiation that is visible to the human eye and forms part of the electromagnetic spectrum. Light travels through vacuum at about 299,792 kilometers per second and can behave as both a wave and a particle, a duality described by Maxwell’s equations and quantum theory. The visible portion of the spectrum spans roughly 380 to 740 nanometers, with shorter wavelengths carrying more energy.

Light interacts with matter in several ways. It can be reflected, refracted, absorbed, transmitted, or scattered. The color observed from a surface arises from the wavelengths that are reflected or transmitted to the eye, while the rest are absorbed. Transparent and translucent materials transmit light with varying degrees of absorption, whereas opaque materials absorb most of the incident light and may reflect or scatter a portion of it.

Perception of light depends on the human visual system. The eye contains rods and cones that detect brightness and color, enabling vision across a broad range of conditions. Other aspects of light, such as intensity and color, are quantified with units like lux (illuminance) and lumen (luminous flux), in contrast to radiometric measures that describe physical power independent of perception.

Light sources include natural sources such as the sun and artificial sources like incandescent lamps, LEDs, and lasers. Beyond illumination, the study of light underpins technologies in imaging, spectroscopy, fiber-optic communication, astronomy, and photography, as well as various scientific and industrial applications.