Louis de Broglie

Louis-Victor-Pierre-Raymond, 7th duc de Broglie, FRS ( 15 August 1892 – 19 March 1987) was a French physicist and a Nobel laureate. He was the sixteenth member elected to occupy seat 1 of the Académie française in 1944, and served as Perpetual Secretary of the Académie des sciences, France.  – He was born to a noble family in Dieppe, Seine-Maritime, younger son of Victor, 5th duc de Broglie. He became the 7th duc de Broglie upon the death without heir in 1960 of his older brother, Maurice, 6th duc de Broglie, also a physicist. He did not marry. When he died in Louveciennes, he was succeeded as duke by a distant cousin, Victor-François, 8th duc de Broglie.

De Broglie had originally intended a career in humanities, and received his first degree in history. Afterwards, though, he turned his attention toward mathematics and physics and received a degree in physics. With the outbreak of the First World War in 1914, he offered his services to the army in the development of radio communications.

His 1924 , Recherches sur la théorie des quanta (Research on the Theory of the Quanta), introduced his theory of electron waves. This included the wave-particle duality theory of matter, based on the work of Max Planck and Albert Einstein on light. The thesis examiners, unsure of the material, passed his thesis to Einstein for evaluation who endorsed his wave-particle duality proposal wholeheartedly; de Broglie was awarded his doctorate. This research culminated in the de Broglie hypothesis stating that any moving particle or object had an associated wave. De Broglie thus created a new field in physics, the mécanique ondulatoire, or wave mechanics, uniting the physics of energy (wave) and matter (particle). For this he won the Nobel Prize in Physics in 1929.

In his later career, de Broglie worked to develop a causal explanation of wave mechanics, in opposition to the wholly probabilistic models which dominatequantum mechanical theory; it was refined by David Bohm in the 1950s.

In addition to strictly scientific work, de Broglie thought and wrote about the philosophy of science, including the value of modern scientific discoveries.

De Broglie' vision of Bohr's atom. The diagram above illustrates an electron standing wave vibrating in an orbit around a nucleus of an atom. Only integral numbers of wavelengths are allowed. If a string is fixed on both ends, then the only waves that can occur are those with zero amplitude at those fixed ends; such points of zero amplitude are called nodes. These vibrations are called standing waves.

De Broglie became a member of the Académie des sciences in 1933, and was the academy’s perpetual secretary from 1942. On 12 October 1944, he was elected to the Académie française, replacing mathematician Émile Picard. Because of the deaths and imprisonments of Académie members during the occupation and other effects of the war, the Académie was unable to meet the quorum of twenty members for his election; due to the exceptional circumstances, however, his unanimous election by the seventeen members present was accepted. In an event unique in the history of the Académie, he was received as a member by his own brother Maurice, who had been elected in 1934. UNESCO awarded him the first Kalinga Prize in 1952 for his work in popularizing scientific knowledge, and he was elected a Foreign Member of the Royal Society on 23 April 1953. In 1961 he received the title of Knight of the Grand Cross in the Légion d’honneur. De Broglie was awarded a post as counselor to the French High Commission of Atomic Energy in 1945 for his efforts to bring industry and science closer together. He established a center for applied mechanics at the Henri Poincaré Institute, where research into optics, cybernetics, and atomic energy were carried out. He inspired the formation of the International Academy of Quantum Molecular Science and was an early member.

The de Broglie hypothesis:

“The fundamental idea of [my 1924 thesis] was the following: The fact that, following Einstein’s introduction of photons in light waves, one knew that light contains particles which are concentrations of energy incorporated into the wave, suggests that all particles, like the electron, must be transported by a wave into which it is incorporated… My essential idea was to extend to all particles the coexistence of waves and particles discovered by Einstein in 1905 in the case of light and photons.” “With every particle of matter with mass m and velocity v a real wave must be ‘associated'”, related to the momentum by the equation:

\lambda = \frac{h}{p} = \frac {h}{{m}{v}} \sqrt{1 - \frac{v^2}{c^2}}

where λ is the wavelength, h is the Planck constant, p is the momentum, m is the rest mass, v is the velocity and c is the speed of light in a vacuum.

This theory set the basis of wave mechanics. It was supported by Einstein, confirmed by the electron diffraction experiments of Davisson and Germer, and generalized by the work of Schrödinger.

However, this generalization was statistical and was not approved of by de Broglie, who said “that the particle must be the seat of an internal periodic movement and that it must move in a wave in order to remain in phase with it was ignored by the actual physicists [who are] wrong to consider a wave propagation without localization of the particle, which was quite contrary to my original ideas.”

From a philosophical viewpoint, this theory of matter-waves has contributed greatly to the ruin of the atomism of the past. Originally, de Broglie thought that a real wave (i.e., having a direct physical interpretation) was associated with particles. In fact, the wave aspect of matter was formalized by a wavefunctiondefined by the Schrödinger equation, which is a pure mathematical entity having a probabilistic interpretation, without the support of real physical elements. This wavefunction gives an appearance of wave behavior to matter, without making real physical waves appear. However, until the end of his life de Broglie returned to a direct and real physical interpretation of matter-waves, following the work of David Bohm. The de Broglie-Bohm theory is today the only interpretation giving real status to matter-waves and representing the predictions of quantum theory. But, since it has some problems and doesn’t go further in its predictions than the Copenhagen interpretation, it is little recognized by the scientific community.

Edited from Wikipedia

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