A form of ripple tank is described in which the point source of waves is simply a succession of periodic air blasts directed downward onto the surface of the water. Two or more such sources can be used simultaneously and their positions are readily changed from place to place. For the production of rectilinear waves a pulsating linear vibrator is described. For the study and projection of water waves an adjustable stroboscope is used, which can either be driven in strict synchronism and in any desired phase relation with the air blasts, or slowly advanced in one direction or the other. Thus the wave images can be made to advance or retreat across the screen and to stop at any desired stage.
The series of photographs show some of the possibilities of the device in demonstrating reflection, refraction, interference, and diffraction of waves.