1) Interference occurs when two waves superpose to form a resultant wave of greater, lower, or equal amplitude. Newton's rings experiment demonstrates interference using a plano-convex lens on a glass plate where concentric bright and dark rings appear. 2) Polarization is when light vibrations are restricted to one plane. It can be produced through reflection, refraction, or double refraction. A diffraction grating uses a series of parallel slits to diffract light into different orders, with the grating equation relating grating spacing to diffraction angle and wavelength. 3) A spectrometer uses a diffraction grating to determine the wavelength of monochromatic light by measuring the diffraction angle of the first order maximum