An anti-reflective coating is a thin film applied to various optical surfaces, such as lenses and mirrors, designed to minimize the amount of incident light that is reflected away from the surface. These coatings function by exploiting the principles of thin-film interference. By carefully controlling the coating's refractive index and thickness—often engineering it to quarter-wavelength dimensions—the reflected light waves are intentionally manipulated so that they are out of phase. This constructive interference causes the reflected light to cancel itself out, maximizing the transmission of light through the material and enhancing the optical efficiency of the surface.