W.2(1) - VIBRATIONS IN A STRING - MELDE'S EXPERIMENT

An electrically driven oscillator (60 Hz) has a string attached to it and stretched across to a small bearing wheel and down, where different masses can be hung. As the oscillator is turned on, standing waves of many orders can be obtained by varying the weight and/or the sring's length. A stroboscopic light shining on the vibrating string makes a very interesting effect. Both apparatuses do not offer good visibility for a larger lecture room. The demonstration can also be done with a mechanical oscillator driven by a function generator, thus allowing one to also vary the oscillation frequency.

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W.2(2) - STANDING WAVES ACROSS TWO DIFFERENT MEDIUMS

Using the same set-up of the previous demonstration - Melde's Experiment - the behavior of a wave travelling through different mediums, can be observed. To the string attached to the electric oscillator, another string of different mass is tied. A wave travelling through the first string will change frequency and amplitude as it goes through the second one.

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W.2(3) - CHLADNI'S SAND FIGURES

A thin square or circular metal plate is clamped by its central axis, to the lecture table. Sand is sprinkled evenly over the top surface. While touching the rim at two seperate points, a violin bow is drawn over he edge, producing Chladni's Sand figures: a series of nodal lines appearing at the points of no vibration.

Click here to download the video clip of this demo