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Jules Lissajous entered the École Normale Supérieure in 1841. Afterwards he became professor of mathematics at the Lycée Saint-Louis. In 1850 he was awarded a doctorate for a thesis on vibrating bars using Chladni's sand pattern method to determine nodal positions. In 1874 Lissajous became rector of the Academy at Chambéry, then in 1875 he was appointed rector of the Academy at Besançon.
Lissajous was interested in waves and developed an optical method for studying vibrations. At first he studied waves produced by a tuning fork in contact with water. In 1855 he described a way of studying acoustic vibrations by reflecting a light beam from a mirror attached to a vibrating object onto a screen.
Duhamel had tried to demonstrate these vibrations with a mechanical linkage but Lissajous wanted to avoid the problems caused by the linkage. He obtained Lissajous figures by successively reflecting light from mirrors on two tuning forks vibrating at right angles. The curves are only seen because of persistence of vision in the human eye.
Lissajous studied beats seen when his tuning forks had slightly different frequencies, in this case a rotating ellipse is seen.
Lissajous was awarded the Lacaze Prize in 1873 for his work on the optical observation of vibration.
Helmholtz used Lissajous' instruments in his study of string vibrations.
Article by: J J O'Connor and E F Robertson
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