The versatile apparatus may be used as demonstration model with an overhead projector or as an economical method of allowing pupils to carry out their own investigations. Four legs are provided enabling the tank to also be used as a free standing bench model. Facilities are provided for mounting a ripple tank illuminant. A gantry is supplied for supporting a motor beam, the height of which is adjustable allowing it to be positioned for maximum effect. Ripples are produced by small 1.5V to 4.5V D.C. motor mounted on the wooden beam of 240 mm length. A cam is fitted to the motor spindle to give an oscillatory motion and a row of nine holes in the beam are for mounting the spherical dippers for production of circular ripples.