Fraunhofer Diffraction at Multiple Slits
The intensity in a Fraunhofer diffraction pattern for multiple slits is given by:[more]
where is the wavelength of the light, is the distance of the diffracting slit from the screen, is the distance between slits, is the width of the diffracting slit, is the range of the diffraction pattern on the screen (measured from the center of the space between the edges of the geometrical shadow) and is the number of diffracting slits. The abbreviation a.u. means arbitrary units.[less]
 A. N. Mateev, Optics, Moscow: Mir Publishers, 1988.
 F. A. Jenkins and H. E. White, Fundamentals of Optics, 3rd ed., New York: McGraw–Hill, 1957.