James Underwood and Eric Gullikson used the Calibration and Standards Beamline at the Advanced Light Source to measure scattering from multilayer mirrors.
Interference is a fundamental consequence of the wave nature of light.
Where the glass of a camera lens meets the air, for example, light is reflected and does not reach the film, but an optical coating of the right thickness can cancel the reflection. A stack of layers of two different materials can also be designed to boost reflectivity instead of canceling it, so that light reflected at each interface constructively interferes with light reflected from other interfaces. The amplified reflection offsets losses due to absorption. In visible light there's a whole cookbook of designs for thin-film reflective coatings. The idea of mirrors that could reflect x-rays and EUV at normal incidence by using constructive interference to amplify weak reflections was suggested in the early 1920s, long before their fabrication was practical.