A Fabry-Pérot Interferometer is an optical device that uses multiple reflections between two parallel mirrors to create interference patterns. When light enters the interferometer, it reflects back and forth between the mirrors, generating constructive and destructive interference. This results in a series of bright and dark fringes, which can be analyzed to determine the wavelength of the light. These devices are commonly used in various fields, including spectroscopy and telecommunications, to measure small changes in wavelength or to filter specific light frequencies. The precision of the Fabry-Pérot Interferometer makes it valuable for scientific research and industrial applications.