Developed by John Koser, the diffraction arc allows students to visualize the diffraction pattern without relying on a screen or wall. Precise incremental degrees can be read of the large protractor. Use the included diffraction grating or blank CDs or DVDs you provide to create different diffraction patterns. Each set includes one diffraction arc, diffraction grating and small mirror with instructions. Required but not included is a laser pointer. Grades 9–12.