I have been using this sheet to teach students how to draw the principal rays for concave and convex mirrors forever, as in before my current students were born. I think it might be time to redraw it; I no longer have the original. But it works so well! I feel, in my bones, the old, old mimeographs that I got when I went to high school in the 1980s. I really like it. I know it. I know its strengths and its weaknesses. I remember making it on my old Mac laptop. And the students are able to draw the diagrams after we use it. So maybe I shouldn't change it?
