Learning goal: to understand multislit interference and how it leads to the design of diffraction gratings. diffraction gratings are used in modern spectrometers to separate the wavelengths of visible light. the working of a diffraction grating may be understood through multislit interference, which can be understood as an extension of two-slit interference. in this problem, you will follow the progression from two-slit to many-slit interference to arrive at the important equations describing diffraction gratings. a typical diffraction grating consists of a thin, opaque object with a series of very closely spaced slits in it. (there are also reflection gratings, which use a mirror with nonreflecting lines etched into it to provide the same effects.) to see how a diffraction grating can separate different wavelengths within a spectrum, we will first consider a "grating" with only two slits. recall that the angles θ for constructive interference from a pair of slits are given by the equation dsin(θ)=mλ, where d is the separation between the slits, λ is the wavelength of the light, and m is an integer.