An old experiment revisited: the Doppler effect in a ripple tank

Studying waves on a water surface, in this paper we present an approach to the Doppler effect that enables students to not only perceive it qualitatively, but also to construct experimentally the well known quantitative relations, which are usually introduced in a rather formal way. The interpretation of these relations is then obtained and discussed exploiting space–time diagrams, whose role is emphasized especially in view of extending this approach to phenomena involving light.