Diffraction Orders

light passing through a slit that is small in comparison to the light wavelength shows a center intensity peak and then a group of peaks on either side of gradually decreasing intensity as the peaks get farther from the center peak. Each peak is a diffraction order, the center peak is order 0 and each peak to the right is numbered +1, +2, +3, etc. in sequence, to the left the peaks are -1, -2, -3, etc. in sequence.