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In most secondary physics textbooks, waves are first introduced with examples of mechanical waves because they can be illustrated by drawings and photographs. However, these illustrations are static and cannot reflect the dynamic nature of waves. Although many mechanical waves (e.g. water waves and vibrating strings) can be easily shown using school apparatus, their motions are too rapid to observe clearly. Computer simulation is a solution but is not 'real'. This article describes how a consumer-type high-speed digital camera can be used visually slowing the motion of some wave experiments. Several techniques to further improve the visibility of the video content are also described.

In this article, we describe a simple method which can be used to measure the efficiency of a low power dc motor, a motor-converted dynamo and a coupled motor–dynamo module as a function of the speed of rotation. The result can also be used to verify Faraday's law of electromagnetic induction.