Hochreflektierend

Hochreflektierend describes surfaces with high reflectivity, i.e., a large fraction of incident light is reflected. Reflectivity is the ratio of reflected to incident power and is wavelength-dependent. The term applies to polished metals, dielectric coatings, and other materials, and can refer to specular (mirror-like) or diffuse reflectance.

In optics, specular reflectance yields clear images, while diffuse reflectance produces even illumination. Reflectance spectra show how reflectivity changes across wavelengths, from UV to infrared, and depend on the angle of incidence and surface roughness.

Common hochreflektierend materials include metal films such as silver and aluminum, often with protective overcoats, and dielectric multilayer coatings designed to achieve very high reflectance at a chosen wavelength. Dielectric mirrors can exceed 99.9% reflectance; metals offer broad, but wavelength-dependent, high reflectivity. Surface condition and contamination reduce performance.

Applications span telescopes and laser optics, solar reflectors and thermal management, architectural surfaces for daylighting and energy efficiency, and calibration standards for optical instruments.

Practical considerations include wavelength specificity, angular dependence, durability, and aging. Oxidation, tarnishing, and cleaning can alter reflectivity, so coatings are chosen for stability and the intended operating environment.