With the slit being completely open, however, the space between the slits (\(d\)) goes to zero, and the number of slits (\(n\)) goes to infinity. The Fraunhofer diffraction formula is an equation that describes the intensity distribution of the diffraction pattern produced by a wave passing through a single slit or a circular aperture. This number can then be used in calculations for the angle at which bright fringes are seen. One way to think of this is to go back to the diffraction grating case, expressed in Equation 3.3.2. Diffraction can be observed in various types of waves, such as sound waves, water waves, and electromagnetic waves including light. Of course such a number can be converted into a slit separation: If a diffraction grating has a grating density of 100 slits per cm c m, then the slits must be separated by d 1100cm 104m d 1 100 c m 10 4 m. To compute the intensity of the interference pattern for a single slit, we treat every point in the slit as a source of an individual Huygens wavelet, and sum the contributions of all the waves coming out at an arbitrary angle. Another important case in which sound waves bend or spread out is called refraction. Significantly more math is required to deal with the intensity of the bright fringes. Sound - Refraction, Frequency, Wavelength: Diffraction involves the bending or spreading out of a sound wave in a single medium, in which the speed of sound is constant. The bright fringes only approximately follow the same spacing pattern, not exactly located halfway between the dark fringes, but using the pairwise approach doesn't tell us much about the intensity of those bright regions, for the same reason it didn't for the central bright fringe – constructive pairs will not be in phase with other constructive pairs. School Sound Formula, Definition, Equations At its core, sound is a result of vibrations that propagate through a medium, typically air, although it can also travel through liquids and solids.