 Numerical approximations may be used, including the Fresnel and Fraunhofer approximations.Because diffraction is the result of addition of all waves (of given wavelength) along all unobstructed paths, the usual procedure is to consider the contribution of an infinitesimally small neighborhood around a certain path (this contribution is usually called a wavelet) and then integrate over all paths (= add all wavelets) from the source to the detector (or given point on a screen).Thus in order to determine the pattern produced by diffraction, the phase and the amplitude of each of the wavelets is calculated.