In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when the diffraction pattern is viewed at a long distance from the diffracting object and also when it is viewed at the focal plane of an imaging lens. If the aperture is in the x'y' plane, with the origin aperture and is illuminated by a monochromatic wave of wavelength lamda, wavenumber k with complex amplitude A(x', y')