Diffraction patterns from multiple slits have envelopes determined by the single slit diffraction pattern. For a single slit the pattern is given by:
:where ? is the diffraction angle, d is the slit width, and ? is the wavelength. For multiple slits, the pattern is
:where q is the number of slits, and g is the grating constant. The first factor, the single-slit result I₁, modulates the more rapidly varying second factor that depends upon the number of slits and their spacing.

Estimation