The slitfilm is a versatile sheet with various single-, double-, and multiple-slit configurations for investigating one dimensional interference patterns. The image below shows the arrangement of slits in the slitfilm. The left column is single slits of decreasing width. The second column is a double slit that continuously widens then abruptly switches to a single slit which continuously becomes thinner. The middle column is multiple-slit, or grating, configurations of varying slit spacing. The fourth column consists of identical slits with identical spacing but increasing numbers of slits. The final column contains double slits of increasing spacing (note that the first slit in this column has zero spacing and thus is simply a single slit and is identical to the thinnest single slit in the first column).
The single-slit interference patterns for the .088, .176, .352, and .704 mm slit widths are below (in that order of increasing slit width). The large central bright spot and evenly-spaced dark spots (intensity minima) are characteristic of single-slit interference patterns.
The next set of images are the interference patterns for the gratings, of slit spacing .033, .066, .088, .132, and .176 mm. For any multiple-slit configuration (including double slits, shown below), the interference pattern consists of evenly-spaced bright spots, or intensity maxima. All of the math and physics is based on the locations of the maxima, whereas for single-slit interference patterns it was all based on the locations of the minima. As a result, the large central bright spot characteristic of single-slit interference patterns is absent in multiple-slit interference patterns.
Zooming in on the last image (.704 mm slit spacing) to show the fine interference pattern:
An interesting comparison is to compare the interference patterns of the single slit of .176 mm width and the grating and double slit of .176 mm slit spacing (presented in that order):
The fact that these are so similar, especially the latter two, is further proof that physics is witchcraft.