Physics Help Forum Diffraction through Grating

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 Sep 23rd 2010, 04:58 AM #1 Junior Member   Join Date: Jun 2010 Posts: 3 Diffraction through Grating Hi, I performed the diffraction grating experiment in the Physics Lab a few days ago and obtained the folowing measurements. The aim was to find the number of slits on the grating given the wavelength of laser employed. I find the readings coherent among themeselves but incoherent as a whole with respect to the task at hand i.e. the value of the number of slits obtained by each reading in a set of observation differs by an order of 10. I know its wrong, still I find my observations precise, can anyone tell me the reason. I know that I'd have to do the whole thing again, still I am interested in finding out what error I commited. NB: You can see that the readings in bold face are quite close but quite far apart when it comes to comparing with the individual "set". ATTACHED: N-No. of slits in grating L-Distance from central bright fringe to the point of maxima Distance between Order of maxima Distance between tan Ø sin Ø grating and source (n) maxima points (L/D) (D) (2L) 1. 12 1 50 2.083 0.901 2. 12 2 109 4.541 0.976 3. 12 3 188 7.834 0.991 1. 13 1 54 2.076 0.900 2. 13 2 117 4.50 0.9761 3. 13 3 203 7.80 0.9918 1. 14 1 58 2.071 0.9004 2. 14 2 125 4.464 0.975 3. 14 3 216 7.712 0.9916 1. 15 1 62 2.066 0.9000 2. 15 2 134 4.466 0.9758 3. 15 3 233 7.766 0.9918 1. 20 1 82 2.055 0.89876 2. 20 2 177 4.425 0.9754 1. 25 1 103 2.06 0.89960 2. 25 2 221 4.42 0.9753 1. 30 1 124 2.066 0.90015 2. 30 2 265 4.416 0.97530

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