Louis de Broglie was the sixteenth member elected to occupy seat 1 of the Académie française in 1944, and served as Perpetual Secretary of the French Academy of Sciences.[10][11] De Broglie became the first high-level scientist to call for establishment of a multi-national laboratory, a proposal that led to the establishment of the European Organization for Nuclear Research (CERN).[12]
Louis de Broglie belonged to the famous aristocratic family of Broglie, whose representatives for several centuries occupied important military and political posts in France. The father of the future physicist, Louis-Alphonse-Victor, 5th duc de Broglie, was married to Pauline d’Armaille, the granddaughter of the Napoleonic General Philippe Paul, comte de Ségur and his wife, the biographer, Marie Célestine Amélie d'Armaillé. They had five children; in addition to Louis, these were: Albertina (1872–1946), subsequently the Marquise de Luppé; Maurice (1875–1960), subsequently a famous experimental physicist; Philip (1881–1890), who died two years before the birth of Louis, and Pauline, Comtesse de Pange (1888–1972), subsequently a famous writer.[13]
Louis was born in Dieppe, Seine-Maritime. As the youngest child in the family, Louis grew up in relative loneliness, read a lot, and was fond of history, especially political. From early childhood, he had a good memory and could accurately read an excerpt from a theatrical production or give a complete list of ministers of the Third Republic of France. For this, he was predicted to become a great statesman in the future.[14]
De Broglie had intended a career in humanities, and received his first degree (licence ès lettres) in history. Afterwards he turned his attention toward mathematics and physics and received a degree (licence ès sciences) 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.
After graduation, Louis de Broglie joined the engineering forces to undergo compulsory service. It began at Fort Mont Valérien, but soon, on the initiative of his brother, he was seconded to the Wireless Communications Service and worked on the Eiffel Tower, where the radio transmitter was located. Louis de Broglie remained in military service throughout the First World War, dealing with purely technical issues. In particular, together with Léon Brillouin and brother Maurice, he participated in establishing wireless communications with submarines. Louis de Broglie was demobilized in August 1919 with the rank of adjudant. Later, the scientist regretted that he had to spend about six years away from the fundamental problems of science that interested him.[14][15]
His 1924 thesis Recherches sur la théorie des quanta[16] (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. 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). He won the Nobel Prize in Physics in 1929 "for his discovery of the wave nature of electrons".[17]
In his later career, de Broglie worked to develop a causal explanation of wave mechanics, in opposition to the wholly probabilistic models which dominate quantum mechanical theory; it was refined by David Bohm in the 1950s. The theory has since been known as the De Broglie–Bohm theory.
In addition to strictly scientific work, de Broglie thought and wrote about the philosophy of science, including the value of modern scientific discoveries. In 1930 he founded the book series Actualités scientifiques et industrielles published by Éditions Hermann.[18]
De Broglie became a member of the Académie des sciences in 1933, and was the academy's perpetual secretary from 1942. He was asked to join Le Conseil de l'Union Catholique des Scientifiques Francais, but declined because he was non-religious.[19][20] In 1941, he was made a member of the National Council of Vichy France.[21] 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.[22]
Louis never married. When he died on 19 March 1987 in Louveciennes at the age of 94,[6] he was succeeded as duke by a distant cousin, Victor-François, 8th duc de Broglie. His funeral was held 23 March 1987 at the Church of Saint-Pierre-de-Neuilly.[23]
Los trabajos de Albert Einstein sobre el efecto fotoeléctrico demostraron que las ondas electromagnéticas están formadas por partículas elementales llamadas fotones. En sentido inverso, el francés Louis De Broglie predijo en 1924 que los corpúsculos materiales del exterior de los átomos, los electrones, deberían mostrar también un comportamiento ondulatorio. La constatación experimental de la dualidad de partícula y onda de los electrones, que llegó pocos años después, cerró el círculo de una de las propuestas más seductoras de la física cuántica: todo lo que existe es, al mismo tiempo, onda y materia.
Materia y ondas
Las controversias sobre la naturaleza de la luz que habían centrado los debates científicos durante más de dos siglos se resolvieron en 1905 cuando Albert Einsten, en su interpretación del efecto fotoeléctrico (ver t59), vino a conciliar las dos hipótesis manejadas y, hasta entonces, consideradas incompatibles:
La ondulatoria, según la cual la radiación luminosa es simplemente una perturbación que se desplaza en el espacio.
La corpuscular, que sostenía que la luz está formada por corpúsculos materiales capaces de interaccionar con la materia.
Einstein concluyó que la luz y, por extensión, las ondas electromagnéticas son a la vez corpúsculo y onda, ya que están formadas por partículas sin masa y sin carga, llamadas fotones, que se propagan en el espacio como un movimiento ondulatorio, intercambiando energía con el entorno.
En un estudio especulativo, que no respondía a ninguna realidad observada que hubiera de explicarse, el francés Louis de Broglie (1892-1987) elucubró con la posibilidad de que, al igual que los fotones, también los electrones tuvieran esa misma dualidad de onda y corpúsculo.
Ondas de De Broglie
En un trabajo publicado en 1924, De Broglie partía de una comparación entre las propiedades del fotón y el electrón para suponer que esta última partícula podría poseer relaciones de energía-frecuencia y longitud de onda-momento lineal análogas a la primera, y expresadas como:
siendo un vector unitario que comparte dirección y sentido con el vector de onda.
Partiendo de las hipótesis relativistas, se podría establecer una equivalencia entre energía y el momento lineal del electrón considerado como onda y como partícula material, de lo que se deduciría que:
Longitud de onda de De Broglie
De la comparación de las magnitudes del comportamiento del electrón entendido como onda y como partícula, se obtiene un valor para la longitud de onda que tendría el movimiento ondulatorio asociado al electrón que viene dado por:
donde v es la velocidad de la partícula y m su masa. Esta magnitud, llamada longitud de onda de De Broglie, aumenta al disminuir la velocidad, y a la inversa.
Si se aplica al postulado del modelo atómico de Bohr (ver t60), que sostiene que las órbitas de los electrones en los átomos sólo pueden tener ciertos radios cuantificados, se deduce que:
Según esta fórmula, las órbitas permitidas (estacionarias) en el modelo de Bohr serían aquellas cuyo radio fuera igual a un número entero de longitudes de onda de De Broglie.
Al igual que para detectar un comportamiento ondulatorio en la luz era preciso manejar dimensiones del orden de su longitud de onda (por ejemplo, rejillas que provocaran patrones de difracción a modo de interferencias luminosas), para observar los efectos de las ondas asociadas a la materia se han de usar partículas de masa pequeñísima y que se desplacen a baja velocidad, por ejemplo, los propios electrones. En estas partículas sería posible obtener valores de la longitud de onda de De Broglie del orden de algunas décimas de nanómetro.
Ilustración gráfica de la regla de cuantificación de Bohr y la longitud de onda de De Broglie para el electrón.
Validación experimental
La primera evidencia experimental de la existencia de las ondas de materia que había predicho De Broglie llegó en 1927, cuando los estadounidenses Clinton Davisson (1881-1958) y Lester Germer (1896-1971) y el inglés George Thomson (1892-1975), en trabajos independientes, determinaron el valor de la longitud de onda de De Broglie según las predicciones de esta teoría.
En esencia, los experimentos realizados se basaban en la hipótesis de que si los electrones pudieran comportarse como ondas, un haz de estas partículas que incidiera sobre un cristal debería producir diagramas de difracción análogos a los observados para los rayos X. Cuando se obtuvieron patrones de difracción para los electrones, se consideró demostrado que estas partículas, al igual que los fotones, se manifiestan tanto a través de sus propiedades corpusculares (materia) como ondulatorias (onda). La hipótesis de la dualidad corpúsculo-onda de la materia se extendió en años posteriores a todos los tipos de partículas elementales y sus agregados (núcleos y átomos).
Louis de Broglie (born August 15, 1892, Dieppe, France—died March 19, 1987, Louveciennes) was a French physicist best known for his research on quantum theory and for predicting the wave nature of electrons. He was awarded the 1929 Nobel Prize for Physics.
Early life
De Broglie was the second son of a member of the French nobility. From the Broglie family, whose name is taken from a small town in Normandy, have come high-ranking soldiers, politicians, and diplomats since the 17th century. In choosing science as a profession, Louis de Broglie broke with family tradition, as had his brother Maurice (from whom, after his death, Louis inherited the title of duke). Maurice, who was also a physicist and made notable contributions to the experimental study of the atomic nucleus, kept a well-equipped laboratory in the family mansion in Paris. Louis occasionally joined his brother in his work, but it was the purely conceptual side of physics that attracted him. He described himself as “having much more the state of mind of a pure theoretician than that of an experimenter or engineer, loving especially the general and philosophical view.” He was brought into one of his few contacts with the technical aspects of physics during World War I, when he saw army service in a radio station in the Eiffel Tower.
De Broglie’s interest in what he called the “mysteries” of atomic physics—namely, unsolved conceptual problems of the science—was aroused when he learned from his brother about the work of the German physicists Max Planck and Albert Einstein, but the decision to take up the profession of physicist was long in coming. He began at 18 to study theoretical physics at the Sorbonne, but he was also earning his degree in history (1909), thus moving along the family path toward a career in the diplomatic service. After a period of severe conflict, he declined the research project in French history that he had been assigned and chose for his doctoral thesis a subject in physics.
In this thesis (1924) de Broglie developed his revolutionary theory of electron waves, which he had published earlier in scientific journals. (Seede Broglie wave.) The notion that matter on the atomic scale might have the properties of a wave was rooted in a proposal Einstein had made 20 years before. Einstein had suggested that light of short wavelengths might under some conditions be observed to behave as if it were composed of particles, an idea that was confirmed in 1923. The dual nature of light, however, was just beginning to gain scientific acceptance when de Broglie extended the idea of such a duality to matter. (Seewave-particle duality.)
de Broglie wavelengthBrian Greene discusses the famous double-slit experiment and explains the formula that connects particles and waves: the de Broglie wavelength equation. This video is an episode in Greene's Daily Equation series.
De Broglie’s proposal answered a question that had been raised by calculations of the motion of electrons within the atom. Experiments had indicated that the electron must move around a nucleus and that, for reasons then obscure, there are restrictions on its motion. De Broglie’s idea of an electron with the properties of a wave offered an explanation of the restricted motion. A wave confined within boundaries imposed by the nuclear charge would be restricted in shape and, thus, in motion, because any wave shape that did not fit within the atomic boundaries would interfere with itself and be canceled out. In 1923, when de Broglie put forward this idea, there was no experimental evidence whatsoever that the electron, the corpuscular properties of which were well established by experiment, might under some conditions behave as if it were radiant energy. De Broglie’s suggestion, his one major contribution to physics, thus constituted a triumph of intuition.
The first publications of de Broglie’s idea of “matter waves” had drawn little attention from other physicists, but a copy of his doctoral thesis was sent to Einstein, whose response was enthusiastic. Einstein stressed the importance of de Broglie’s work both explicitly and by building further on it. In this way the Austrian physicist Erwin Schrödinger learned of the hypothetical waves, and on the basis of the idea, he constructed a mathematical system, wave mechanics, that has become an essential tool of physics. Not until 1927, however, did Clinton Davisson and Lester Germer in the United States and George Thomson in Scotland find the first experimental evidence of the electron’s wave nature.
After receiving his doctorate, de Broglie remained at the Sorbonne, becoming in 1928 professor of theoretical physics at the newly founded Henri Poincaré Institute, where he taught until his retirement in 1962. He also acted, after 1945, as an adviser to the French Atomic Energy Commissariat.
Get Unlimited Access
Try Britannica Premium for free and discover more.
In addition to winning the Nobel Prize for Physics, de Broglie received, in 1952, the Kalinga Prize, awarded by the United NationsEconomic and Social Council, in recognition of his writings on science for the general public. He was a foreign member of the British Royal Society, a member of the French Academy of Sciences, and, like several of his forebears, a member of the Académie Française.
De Broglie’s keen interest in the philosophical implications of modern physics found expression in addresses, articles, and books. The central question for him was whether the statistical considerations that are fundamental to atomic physics reflect an ignorance of underlying causes or whether they express all that there is to be known; the latter would be the case if, as some believe, the act of measuring affects, and is inseparable from, what is measured. For about three decades after his work of 1923, de Broglie held the view that underlying causes could not be delineated in a final sense, but, with the passing of time, he returned to his earlier belief that the statistical theories hide “a completely determined and ascertainable reality behind variables which elude our experimental techniques.”
While learning atomic structure I stumbled upon a very unusual question.
As we know that the energy of a wave is given by the equation: E =hcλ�=ℎ�λ and Louis de broglie wave equation is given by the equation λB=hpλ�=ℎ�. My doubt is that, that is λB=λλ�=λ??. Do the λB,λλ�,λ represent the same thing ??
My teacher equated E=hcλ�=ℎ�λ and E=mc²�=��² to form hcλ=mc²ℎ�λ=��² and rearranged to form λ=hmcλ=ℎ�� and then replaced λλ by λBλΒ and c� by v� for general formula and derived the Louis de broglie equation. This created my doubt in first place and I created another doubt that whether the equation for energy of wave is valid for relativistic equation of E=mc²�=��² because the E=mc²�=��² is for particles while the former is for waves.
Is my understanding correct?? Please help and thanks in advance!
Argomento precedente
.png){kind=small}
.jpg)
Primo 
