Santa Clara University Archives - A Favorite Abode of Science

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«	Pressure Demonstrator	Lissajous figures	»

Acoustic Instrument, Late 19th Century, Newton and Company of London "This unique piece of apparatus uses Lissajous figures to show that the ratio of the frequency ratios in a diatonic scale are ratios of small numbers. On the side is an air-driven vibrating reed with a small mirror attached to its free end. The octagonal, revolving drum contains eight reeds, ranging up the scale from the same frequency as the fixed reed to its octave. In use, the box holding the fixed reed would be rotated 90 degrees, making it oscillate at right angles to the other reeds. A beam of light reflecting from the two reeds in succession undergoes simple harmonic motion in two perpendicular directions, thus producing a Lissajous figure when the beam strikes a screen. The shape of the figures produced by two frequencies which bear small number ratios to each other is well-known." - Historical Physics Teaching Apparatus Item#: 325,977 Photograph courtesy of Steve Turner, National Museum of American History, Smithsonian Institution
©2003 - Permission to reproduce any portion of the exhibit A Favorite Abode of Science is strictly prohibited.
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