Not sure if this is the right forum for this but I am analysing the data for the diffraction experiment I have just done (laser source at two slit diffraction grating) and have got the graph (similar to this http://www.physics.umd.edu/courses/Phys273/williams06/TwoSlit.jpg" [Broken]). However all the minima for my data have been shifted towards the origin when compared to the theoretical plot. I have been racking my brains but can't think of any convincing reasons why this could happen other than the fact that I got bad results. The minima are also not at zero but I am less concerned about this since I am assuming this is just down to not getting perfect intensity. Thanks.