## Sunday, August 15, 2010

### Prince Louis-Victor de Broglie

Prince Louis-Victor de Broglie was born in Dieppe, France on August 15, 1892., the younger son of Victor Duc de Broglie and Pauline d'Armaille. The history of the de Broglie family included service to the French crown for which the head of the family was granted the hereditary title of "Duc" (Duke) by Louis XIV and the German title of "Prinz" (Prince) for service to Austria during the Seven Years War. All of de Broglie's early education was provided by private tutors. In 1906 he was sent to Lycee Janson de Sailly where he spent three years completing his secondary education. De Broglie then went to the Sorbonne where he initially studied history, intending to take a job in the diplomatic service, earning a degree in 1910. Unsatisfied with his studies in the liberal arts de Broglie began studying theoretical physics.

De Broglie graduated with a degree in physics in 1913. Thereafter, as required by French law, de Broglie enlisted in the military. De Broglie served for the duration of the First World War, from 1913 to 1919. In his initial posting he was sent to a fort at Mount Valerien, where he was given very little to do and it was a difficult time for him. Later, with the influence of his brother Maurice, who had succeeded his father as Duc, de Broglie was posted to a radio station at the Eiffel Tower working as an electrician. De Broglie found this posting much more satisfying as it allowed him experience working with electrical equipment, which would serve him well in his scientific career.

After leaving the French service de Broglie worked with his brother Maurice, also a theoretical physicist, taking advantage of the laboratory built by his bother at the family mansion in Paris. At the time physicists thought of matter as being composed of particles and light was thought of as a wave-like phenomena. Albert Einstein, in his description of the photo-electric effect had demonstrated that light can behave both as a particle and a wave. Influenced by Einstein, de Broglie proposed that matter also has a dual nature, as both a particle and a wave. He proposed that the wavelength of matter is equal to Planck's constant divided by the momentum of the particle (wavelength h/p). This is true for all matter, small particles like electrons and large objects such as bullets or cars. Because of the momentum term in the wavelength equation (p) is equal to the mass of an object multiplied by its velocity (p=m*v) the wavelength gets shorter the more massive an object is and it is only for small particles that the wavelength has any practical effect. Using this insight for his doctoral thesis, his committee was unsure of the validity of his ideas and so passed his thesis on to Einstein who wholeheartedly agreed with the work. De Broglie was granted his doctorate in 1923.

De Brolie's insight into the wave nature of matter gave rise to a field of physics called wave mechanics. An electron, traveling around a nucleus, must have a wave pattern that is stable, where the length of the orbital is an integer number of wavelengths long. Erwin Schrodinger used de Broglie's theory of particle waves to work out the solutions to the wave equation that showed the behavior of an electron in a hydrogen atom and these equations agreed with experimental data.

For his discovery of the wave nature of matter de Broglie was awarded the Nobel Prize in physics in 1929. After completing his doctorate de Broglie gave a series of lectures at the Sorbonne, and was appointed professor of theoretical physics at the Poincare Institute in 1926. In 1932 he was appointed chair of theoretical physics at the Sorbonne where he taught until 1962.

De Broglie died on March 19, 1987.

References:

"Biography of Prince Louis-Victor de Broglie the Nobel Prize in Physics 1929" at debroglie.poldow.com

Prince Luis de Broglie Nobel Biography

Luis de Broglie Wikipedia Entry

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