Louis Victor de Broglie

Louis Victor de Broglie (1892-1987), also known as Prince de Broglie, French theoretical physicist who made major contributions to quantum theory. De Broglie was born in Dieppe. He studied history at the Sorbonne, but switched to physics for his doctoral thesis. In this work, published in 1924, he proposed that electrons are associated with what he called “pilot waves”. The converse idea, that electromagnetic waves can behave like particles in certain circumstances, had been proposed by Albert Einstein in 1905 to explain the photoelectric effect.

De Broglie was able to use the pilot wave idea to explain the behaviour of electrons within atoms. The Danish physicist Niels Bohr had shown that the electrons were confined to certain fixed orbits. De Broglie suggested that the wavelength of a “pilot wave” was inversely proportional to the momentum of the electron. The farther from the nucleus an electron was, the lower its momentum and the longer the wavelength of the associated wave. The only possible orbits were those in which a whole number of wavelengths would exactly fit around the orbit, so that a standing wave was formed (see Wave Motion).

In 1927 the British physicist G. P. Thomson, and, independently of him, the American physicists Clinton Davisson and Lester Germer, confirmed de Broglie’s suggestion when they demonstrated wavelike behaviour in beams of electrons. In 1926 de Broglie’s idea was developed by the Austrian physicist Erwin Schrödinger in a wave equation that was fundamental to the future development of quantum theory. Wave-particle duality is now known to be a basic property of matter and energy.

De Broglie taught at the Sorbonne until his retirement in 1962. He was awarded the Nobel Prize for Physics in 1929.