Here's a question from my textbook: "Why do you not see a spectrum of colors when light passes through a flat pane of glass?" However I think that a spectrum of colors will be formed when light passes through a flat pane of glass. The colors will all be parallel to one another, unlike a prism where they are diverging. I think so because at the first face of the flat pane they will all disperse, as happens at the first face of a prism and at the second face they will all be refracted in such a way that they are all parallel to the incident angle and hence parallel to each other. Am I right or do they not disperse? PS: The answer in the textbook is, "Because a flat pane of glass has parallel sides"