Interferometry is a powerful optical technique used to measure minuscule changes in distance, refractive index, or strain by analyzing the interference pattern of light. The fundamental principle involves splitting a monochromatic light beam into two paths, causing the two resulting beams to travel different distances or through different media. When these two beams are recombined, they exhibit interference—a pattern of constructive and destructive wavelengths—whose characteristics are directly dependent on the phase difference between the two beams. By precisely measuring the shift in this interference pattern, extremely high sensitivity can be achieved, allowing for the non-contact determination of physical parameters with sub-nanometer resolution, making it valuable in fields such as metrology, gravitational wave detection, and optical sensing.