This document discusses the phenomenon of diffraction, specifically single slit diffraction. When light passes through a small aperture, the wavefronts spread out in a phenomenon called diffraction. With a single slit, this results in a diffraction pattern of bright and dark fringes on a distant screen. The width of the central bright fringe is determined by the slit width and wavelength of light. A mathematical relationship is derived that expresses the half-angle of the central fringe as being inversely proportional to the slit width and proportional to the wavelength. Examples are given to illustrate how this relationship can be used to determine unknown wavelengths from measured diffraction patterns.