Visualization and interpretation for the electromagnetic derivation of Snell's laws

Veritable snapshots-in-time of the vector fields in the classic problem of plane wave refraction at a planar interface are drawn simply and directly using a contour-plotting routine. These field pictures, together with the antecedent mathematics, give students and teachers a panoramic view of the pertinent wave physics. Classroom examples and computer assignments, based on the methodology of this paper, help to underscore the real physical nature of the subject called electromagnetics.