Paul Langevin (January 23, 1872 - December 19, 1946) was a French physicist.

He was born in Paris, France, and studied at the École de Physique et Chimie and the École Normale Supérieure. He then went to Cambridge University and studied in the Cavendish Laboratory under Sir J. J. Thomson. He returned to the Sorbonne and obtained his Ph.D. from Pierre Curie in 1902. In 1904 he became professor of physics at the Collège de France. In 1926 he became director of the École de Physique et Chimie, where he had been educated. He was elected, in 1934, to the Académie des sciences.

He is noted for his work on paramagnetism and diamagnetism, and devised the modern interpretation of this phenomenon in terms of electric charges of electrons within atoms. His most famous work was in the use of ultrasonic sounds using Pierre Curie's piezoelectric effect. During World War I he began working on the use of these sounds to detect submarines through echo location. However the war was over by the time he had it operational. During his career, Paul Langevin also did much to spread the theory of relativity in France.

In 1917 Paul Langevin, busy inventing sonar that year, made sound in water using electricity to resonate quartz crystals and as a matter of fact invented the crystal oscillator.

He was noted for being an outspoken opponent of Nazism, and was removed from his post by the Vichy government following the occupation of the country by Germany. He was later restored to his position in 1944. He died in Paris a year after living to see his homeland liberated.

References

• Asimov's Biographical Encyclopedia of Science and Technology, Isaac Asimov, Doubleday & Co., Inc., 1972, ISBN 0385177712.

External links

• Wolfram research biographical entry by Michel Barran.