multiple beam interference

Multiple beam interference occurs when light waves reflect multiple times within a thin film or layered structure, such as a soap bubble or anti-reflective coating. These reflected waves can overlap and interfere with each other—either strengthening (constructive interference) or weakening (destructive interference) the reflected light—depending on their phase differences. This interference pattern creates colorful displays or specific reflection and transmission properties. The phenomenon relies on the precise optical path differences of the multiple reflected beams, which are influenced by the film’s thickness, refractive index, and the wavelength of light involved.