The Double Slit Experiment – Single-split experiment

A laser beam hits the single slit.

What happens if we gradually decrease the size of the opening of the slit? We observe that the red dot dissolves, and additional light and dark stripes emerge in the vicinity.

Behind the slit, light thus not only hit the screen following a straight path, but takes all kinds of directions, with fluctuating degrees of intensity, so that we see the stripes at various points on the screen.