A two-way mirror, also called a one-way mirror or observation mirror, is a specialized glass that appears reflective from one side while remaining transparent from the other under specific lighting conditions. This effect is achieved through a thin, partially reflective coating and controlled lighting where the observed area is brightly lit while the observation area remains darkened. The physics relies on light differential rather than special glass construction. Two-way mirrors are commonly used in security monitoring, police interrogation rooms, research facilities, and retail loss prevention. When properly installed, those on the brightly lit side see only their reflection, while observers in the darker area can see through a window.
