French physicist (1822–1880)
Born at Versailles, Lissajous graduated from the Ecole Normale Supérieure in 1847 and then taught physics at a school in Paris.
He was interested in finding a way of making sound vibrations visible. Chladni had already produced his sand-pattern method but this only determined the nodal lines, where there was no vibration. Lissajous's method was to reflect light off mirrors attached to two tuning forks set at right angles. The superposition of the vibrations formed dynamic patterns on a screen, which are now called Lissajous figures. From the form of these curves he could calculate the relative frequencies of the forks and thus provided a precise way of measuring pitch. He also invented the vibrating microscope, which produced Lissajous figures when vibrating objects, such as violin strings, were viewed through it.
