Friday, August 15, 2014

Louis de Broglie and wave nature of matter

Louis de Broglie
(1892 – 1987)
On August 15, 1892, French physicist and Nobel Laureate Louis de Broglie was born. He is best known for making groundbreaking contributions to quantum theory. He postulated the wave nature of electrons and suggested that all matter has wave properties. This concept is known as wave-particle duality or the de Broglie hypothesis.

Louis de Broglie attended the Lycée Janson of Sailly and decided to continue his studies in literature, but then earned his degree in history in 1910. The scientist earned his degree in medicine three years later and was then conscripted for military service and posted to the wireless section of the army. He was stationed at the Eiffel Tower. When World War I was over, de Broglie spent another four years studying physics. He was especially interested in theoretical physics and completed his thesis titled Recherches sur la Théorie des Quanta (Researches on the quantum theory) at the Faculty of Sciences at Paris University and it was known to be highly influenced by the works of Albert Einstein. He later described his interest for theoretical physics: "I was attracted to theoretical physics by the mystery enshrouding the structure of matter and the structure of radiations, a mystery which deepened as the strange quantum concept introduced by Planck in 1900 in his research on black-body radiation continued to encroach on the whole domain of physics". The ideas set out in de Broglie's doctoral thesis, which first gave rise to astonishment owing to their novelty, were subsequently fully confirmed by the discovery of electron diffraction by crystals in 1927 by Davisson and Germer. They served as the basis for developing the general theory nowadays known by the name of wave mechanics, a theory which has utterly transformed our knowledge of physical phenomena on the atomic scale. The concept of matter waves in quantum mechanics reflects the wave–particle duality of matter. The waves became later known as de Broglie waves and in his theory, the scientist shows that the wavelength is inversely proportional to the momentum of a particle. Also, the frequency of matter waves, as deduced by de Broglie, is directly proportional to the total energy E (sum of its rest energy and the kinetic energy) of a particle [1,2].

De Broglie continued his career in publishing further scientific works teaching at Sorbonne. The Institut Henri Poincaré was just built in Paris in this period, and the scientist was offered to teach courses in theoretical physics there. He became the chair of theoretical physics at the Faculty of Sciences at the University of Paris in 1932 and it is known that many French and international students came to work with the brilliant de Broglie, who also supervised numerous doctoral theses [2]. Louis de Broglie devoted his work mostly to the study of the various extensions of wave mechanics. It is known that he put much effort into Dirac's electron theory, the new theory of light, the general theory of spin particles, and applications of wave mechanics to nuclear physics and he authored over 25 books on these various fields of study. In 1929, he was awarded the Henri Poincaré medal at the Academie des Sciences and in the same year, the Swedish Academy of Sciences conferred on him the Nobel Prize for Physics "for his discovery of the wave nature of electrons". The scientist was elected a member of the Academy of Sciences of the French Institute in 1933 and became its Permanent Secretary for the mathematical sciences three years later [1,3].

At yovisto, you may be interested in a short introduction to "What is Quantum" by Dr. John Preskill.



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