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DIFFRACTION GRATING – SIMPLE SPECTROMETER OBJECT To measure the wave length of light with a diffraction grating. APPARATUS Force table spectrometer, diffraction grating, known light source, spirit level. THEORY The wave length of light, λ , can be measured with a diffraction grating of the transmission type using: δ = n λ = S sin θ n (1) where S is the distance between the rulings of the grating, θ is the diffraction angle, and n is the order number. n can have values of 0, 1, 2, 3,…. . these are the orders of the spectra produced n = 0 corresponds to the direct ray (all colors mixed), n = 1 corresponds to the first time the colors appear (separated), n = 2 corresponds to the second time the separated colors appear, etc. Constructive interference occurs when the difference in path length ( δ ) between the two light rays is equal to a multiple of a whole wavelength. See the diffraction grating diagram below. This is the way the colors are spread apart, the different wavelengths will make for a different position for constructive interference in the viewing telescope. Diffraction grating
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This note was uploaded on 08/25/2011 for the course PHYS 164 taught by Professor Johnjames during the Fall '09 term at MO St. Louis.

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