Foucault, Jean Bernard Leon

Foucault, pronounced foo KOH, Jean Bernard Leon, pronounced zhahn behr NAR lay AWN (1819-1868), a French physicist, used a revolving mirror to measure the speed of light. Some types of measuring apparatus still use adaptations of his method. Foucault proved in 1850 that light travels more slowly in water than in air, and that the speed varies inversely with the index of refraction. He also made improvements in the mirrors of reflecting telescopes.

Foucault demonstrated the rotation of the earth on its axis with a pendulum experiment, and also by using a gyroscope that maintained its axis in a fixed direction while the earth turned relative to that direction. Foucault also discovered the existence of eddy currents. These currents are produced in a conductor moving in a magnetic field. Foucault was born in Paris.

Contributor: Richard G. Olson, Ph.D., Prof. of History, Harvey Mudd College.

Foucault, Jean Bernard Leon

Master Index