We use the Cornell slit plates on which there is a wide variety of single, double, and multiple slits that have been photographically reproduced. The student places the slit plate close to their eye and stands many meters away from the light source. The light source consists of two straight-filament showcase lanterns, one inverted above the other. The lower lamp can move in a groove at right angles to the line of sight, and its lateral displacement can be measured quite accurately. The central image of the pattern produced by this lower filament is used as a marker for the various maxima of the pattern produced by the upper filament. The students can thus determine the angular deviation of the maxima for a wide variety of slit patterns in a situation which corresponds quite closely to Frauenhofer diffraction. The secondary maxima in the three and four slit patterns are quite clearly visible. There are also 40 and 80 slit patterns which make possible determinations of the wavelength of red and blue light. The actual dimensions of the slit are determined by projecting the Cornell slit plate in a slide projector, with a known scaling.