The multiple slit arrangement is presumed to be constructed from a number of identical slits, each of which provides light distributed according to the single slit diffractionexpression. The diagram at right illustrates a 5 slit configuration, where the path difference at point P between waves from each of the slits is dsinθ with a slit separation of 'd'.
Multiple Slits Diffraction
Under the Fraunhofer conditions, the light curve (intensity vs position) is obtained by multiplying the multiple slit interference expression times the single slit diffraction expression. King soft app. The multiple slit arrangement is presumed to be constructed from a number of identical slits, each of which provides light distributed according to the single slit diffraction expression. The multiple slit interference typically involves smaller spatial dimensions, and therefore produces light and dark bands superimposed upon the single slit diffraction pattern.
The progression to a larger number of slits shows a pattern of narrowing the high intensity peaks and a relative increase in their peak intensity. This progresses toward the diffraction grating, with a large number of extremely narrow slits. This gives very narrow and very high intensity peaks that are separated widely. Since the positions of the peaks depends upon the wavelength of the light, this gives high resolution in the separation of wavelengths. This makes the diffraction grating like a 'super prism'.