In books 4 and 5 of the De aspectibus Alhacen undertakes an analysis of the principles of reflection that culminates with his approach to ‘Alhazen’s Problem’ in book 5: to find the point or points of reflection in a convex or concave spherical mirror for any randomly posed point of radiation and center of sight. In the process, Alhacen attempts to establish the basic principles of reflection—e.g., that reflection occurs at equal angles within a single plane perpendicular to the reflecting surface, etc.—on the basis of various controlled experiments.
Books 4–5 in 2 volumes
Pp. cxxviii + 699
Interpretatio: Sources and Studies in the History of Science B2