PURPOSE: To show how wave fronts crowd together in front of and spread out behind a moving source.

DESCRIPTION: The single point source can be moved by rotating the support arm on a lazy susan. Moving the source uniformly in one direction demonstrates the Doppler effect in a clear and understandable way.

SUGGESTIONS:

REFERENCES: (PIRA unknown.) Several good film loops and movies can be used which show ripple tank effects very clearly.

EQUIPMENT: Ripple tank with accessories on cart.

SETUP TIME: 5 min.