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 one). 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.