Reflectors

A reflector is a surface or device that redirects electromagnetic waves or particles by reflection. Reflectors can be passive or active, and they operate in domains ranging from visible light to acoustics, radar, and neutrons. Their primary function is to redirect energy, shape wavefronts, or increase visibility.

Optical reflectors include specular surfaces that reflect light like a mirror and diffuse surfaces that scatter light in many directions. Parabolic and spherical reflectors concentrate or collimate light or radio waves. Retroreflective materials are designed to return light toward its source, improving night visibility.

Materials commonly used for optical reflectors include metals such as aluminum and silver, and dielectric coatings for high reflectance with specific spectral properties. Diffuse reflectors use white paints or powdery materials, such as titanium dioxide or barium sulfate, to achieve uniform scattering.

Applications span architecture and daylighting, photography and telescopes, solar concentrators, and communication systems. Road safety relies on retroreflective markers and cat’s-eye devices; parabolic reflectors and dish antennas collect and direct signals; acoustic reflectors shape sound in concert halls and studios; neutron reflectors influence reactor design.

Performance is described by reflectance (the fraction of incident energy reflected), angular and spectral response, and environmental durability. Designers consider surface roughness, aging, and coatings to balance efficiency, cost, and longevity.