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[[image - photo of Prince Louis de Broglie]]
[[photo credit]] Agence Diffusion Presse, Paris [[/photo credit]]
[[caption]] PRINCE LOUIS DE BROGLIE [[/caption]]

researches in nuclear physics, X rays, and radioactivity.

Louis de Broglie studied at the Lycée Janson-de-Sailly and received his baccalauréat in history in 1909 from the Sorbonne. However, he has stated in an interview with André Gillois, which is recorded in Que Etes Vous? (1953): "After passing the examinations in history, I felt that I was more interested in scientific philosophy and in science. . . . I was brought to science by philosophy, by generalizations, and by the books of [Henri] Poincaré." This interest led him to obtain a licence in science in 1913 from the Faculty of Sciences, University of Paris. In this period he was also interested in paleography. 

Mobilized in 1913, de Broglie was assigned to the radio-telegraph branch of the French Engineering Corps. During much of his period of service he worked at the wireless station of the Eiffel Tower in Paris. In 1919 he took up his studies again in the physics laboratory of his elder brother. The subsequent development of his thought was chronicled in "Vue d'ensemble sur mes travaux scientifiques," which he contributed to a commemorative volume in honor of his sixtieth birthday in 1952. In this book, Louis de Broglie, Physicien et Penseur, Nobel Prize winners Albert Einstein, Erwin Schrödinger, Enrico Fermi, Jean Perrin, and Paul Dirac discussed various aspects of his work. 

Niels H. de V. Heathcote, in Nobel Prize Winners in Physics, 1901-1950 (1953), pointed out that until de Broglie's establishment of the wave theory, two contradictory theories were coexistent: Philipp Lenard's, asserting that ultraviolet light falling on a metal plate caused the ejection of electrons, whose energy was completely independent of the intensity of the incidental light, and Einstein's, which assumed that that incidental light transmitted its energy to the electrons in packets equal to hv, with h representing Max Planck's constannt, and v, the frequency of incidental light. 

Such were the puzzles which confronted physicists. This gave de Broglie the idea that "electrons . . . could not be represented as simple corpuscles, but that to them also must be attributed a periodicity. . . ."

"Thus I arrived at the following general idea," stated de Broglie, "which has guided my researches: for matter, just as much as for radiation, in particular light, we must introduce at one and the same time the corpuscle concept and the wave concept . . . it must be possible to establish a certain parallelism between the motion of a corpuscle and the propagation of the wave which is associated with it." 

In this way, explained Heathcote, by attributing wavelike properties to matter, de Broglie "succeeded in representing the motion of the material particle as a combination of waves having slightly different velocities of propagation, at regular intervals . . . the waves would combine to form a wave-crest, the crest disappearing at one point to reappear an instant later at the next. The velocity of the crest - the so-called 'group velocity' - is entirely different from the velocities of the various waves which combine to form the crest. De Broglie identified this group velocity with the velocity of the material particle; the distance between successive crests is the wave length of the 'matter waves' and is known as the de Broglie wave length." 

Charles Mauguin, one the four members of the doctoral jury to which de Broglie presented his doctoral thesis, "Recherches sur la théorie des quanta," at the Sorbonne in 1924, recalls the astonishment and scepticism of his colleagues upon being confronted with this revolutionary concept. In the same year de Broglie was awarded his doctorate. 

The contribution made by de Broglie in establishing the universal connection between particles and waves was obtained "apparently by a process of pure reasoning from mathematical relations suggested by relativity. . . . It stimulated Schrödinger to seek for an explanation of the stationary states of atoms as a resonance phenomenon and led him to his famous wave equation, which is the accurate extension to curved orbits of de Broglie's relations for a particle on a straight course" (Nature, June 6, 1953).

In 1927 came the direct verification of de Broglie's ideas by Clinton J. Davisson and Lester Halbert Germer working with slow electrons, and by G. P. Thomson working with fast electrons, and a new era began in the understanding of atomic processes. "The precise relationship of the waves to the particles remains a subject of controversy; what is established is that one must carry out calculations to determine the motion of the waves and then interpret them in terms of probabilities for the particles" (Nature, June 6, 1953).

De Broglie gave a recapitulation of his work to date at the Congress of Solvay in 1927, for by then, it was already evident that his theory had completely transformed all considerations of atomic phenomena. World-wide attention to