Parabolic mirrors in a solar power plant. (Source: © luchschenF / stock.adobe.com)

A flat or curved object that reflects incident light rays. The mirror can be glass or plastic, coated underneath with a thin layer of metal (aluminium, silver) that reflects the light. Mirrors are used to change the direction of light rays. They are important in solar energy, where arrays of large mirrors, parabolic or flat heliostats, concentrate the sun’s radiation. In laser-driven inertial thermonuclear fusion, mirrors direct laser beams onto a deuterium-tritium target.