👉 Interferometer is a device used to measure light or other electromagnetic waves by observing changes in their phase. It consists of two parallel mirrors, one at each end of a central axis, and an optical system that receives the reflected wave from both mirrors. The phase difference between the reflected and refracted waves can be measured, which indicates the direction of the incident wave. This technique is used for measuring the polarization state of light, as well as other properties such as wavelength and intensity.