Max Laue The Nobel Prize in Physics 1914

biography and work

Crystal diffraction of X-rays
All crystals can be classified into one of seven crystal systems – cubic, tetragonal, trigonal, orthorhombic, monoclinic, and triclinic. Each of these crystal systems is divided into a number of crystal classes. Here we will be looking at the cubic crystal system.

This system is divided into three classes – primitive, body-centered, and face centered. The cubic class is characterized by unit cells having orthogonal faces and sides of equal lengt

Three classes of the cubic crystal system:

Primitive

Body-Centered

Face-Centered

In this experiment the x-ray diffraction pattern from a piece of wire composed of many cubic microcrystals will be analyzed to ascertain the specific cubic class of the microcrystals.

The unit cell dimensions and Avogadro’s number will also be determined. Suppose a monochromatic x-ray beam of wavelength ? is directed with an incident angle, ?, toward N parallel atomic planes separated by a distance d. Here, d is assumed comparable in magnitude to ?. A fraction of the incident beam will be deflected at each of the surfaces with the angle of incidence equal to the angle of reflection, while the remainder of the beam is transmitted. For a given inter-planar spacing, wavelength, and incident angle, beams reflected from successive layers of atoms will, for the most part, emerge from the crystal out of phase and destructively interfere, producing no appreciable reflected x-ray intensity at the corresponding reflection angle. However, if he difference in optical path length for rays reflected from successive planes in a whole number, n, of wavelengths, then the reflected beams will emerge from the crystal in phase and constructively interfere, producing a reflected wave at reflection angle, ?, with an intensity N times stronger than that of a single reflected beam. The diffraction condition is expressed by the Bragg equation. 2d sin ? n = n? n = 1, 2, 3, … (1)



Bragg reflection on a set of N atomic planes. The apparatus used to produce the film you will be studying includes an X-ray generator and powder camera. The x-ray generator produces a dichromatic x-ray beam of wavelengths ? 1 = 1.54050 ? and ? 2 = 1.54434 ?. The intensity weighted average is ? avg = 1.5418 ?. The dichromatic x-ray beam interacts with a piece of wire that rotates within the camera. The wire is composed of very fine microcrystals, which present to the x-ray beam a near infinite variety of crystal orientations. It is therefore highly probable that a set of lattice planes will be oriented to satisfy Bragg’s Law.

Max Laue was born on October 9, 1879 at Pfaffendorf, near Koblenz. He was the son of Julius von Laue, an official in the German military administration, who was raised to hereditary nobility in 1913 and who was often sent to various towns, so that von Laue spent his youth in Brandenburg, Altona, Posen, Berlin and Strassburg, going to school in the three last-named cities. At the Protestant school at Strassburg he came under the influence of Professor Goering, who introduced him to the exact sciences.

In 1898 he left school and for a year did his military service. He then went to the University of Strassburg where he studied mathematics, physics and chemistry; but soon he moved to the University of G?ttingen, where he worked under Professor W. Voigt and Professor W. Abraham, who greatly influenced him. After a semester at the University of Munich he went, in 1902, to the University of Berlin to work under Professor Max Planck. Here he attended lectures by O. Lummer on interference spectroscopy and heat radiation, the influence of which was shown in von Laue's dissertation on interference phenomena in plane-parallel plates. After obtaining his doctorate at Berlin in 1903, von Laue went for two years to the University of G?ttingen. In 1905 he was offered the post of assistant to Max Planck at the Institute for Theoretical Physics at Berlin. Here he worked on the application of entropy to radiation fields and on the thermodynamic significance of the coherence of light waves.

In 1909 he went as Privatdozent to the University of Munich, where he lectured on optics, thermodynamics and the theory of relativity and in 1912 he became Professor of Physics at the University of Zurich. In 1914 he moved, as Professor of Physics, to Frankfurt on Main and from 1916 he was engaged in war work at the University of W?rzburg on high vacuum tubes used for telephony and wireless communication. In 1919 he was appointed Professor of Physics at the University of Berlin, a post which he held until 1943. From 1934 onwards he acted as consultant to the Physikalisch-Technische Reichsanstalt at Berlin-Charlottenburg.

In 1917, when the Institute for Physics was established at Berlin-Dahlem with Einstein as its Director, von Laue had charge, as Second Director, of most of the administrative work of this Institute, which was in close touch with German scientific research. Von Laue exerted, during this period and also later, considerable influence on the development of scientific research in Germany. When Berlin was bombed, this Institute moved to Hechingen, in W?rttemberg and von Laue accompanied it there. He remained at Hechingen from 1944 until 1945 and here, to distract his thoughts from the war, he wrote a History of Physics, which went into four editions and was translated into seven other languages. Here he welcomed the arrival of the French troops and was taken by an Anglo-American mission, together with nine other German scientists, to England where he remained until 1946 During his confinement in England he wrote a paper on the low absorption of X-rays during diffraction, which he contributed in 1948, to the International Union of Crystallographers at Harvard University. In 1946 he went to G?ttingen as Acting Director of the Max Planck Institute and Titular Professor in the University there.

In 1951 he was elected Director of the Fritz Haber Institute for Physical Chemistry at Berlin-Dahlem and here he did much work on X-ray optics in collaboration with Borrmann and others.

In 1958 he retired and in 1959 his 80th birthday was celebrated in Berlin-Dahlem. He lived on, still actively at work, for another six months. Apart from his earlier work already mentioned, von Laue's scientific work extended over a wide field. Early in his career he was greatly excited by Einstein's theory of relativity and between 1907 and 1911 he published eight papers on the application of this theory. In 1911 he published a book on the restricted theory and in 1921 another on the general theory, both books going into several editions His best known work, however, for which he received the Nobel Prize for Physics for 1914, was his discovery of the diffraction of X-rays on crystals. This discovery originated, as he related in his Nobel Lecture, when he was discussing problems related to the passage of waves of light through a periodic, crystalline arrangement of particles. The idea then came to him that the much shorter electromagnetic rays, which X-rays were supposed to be, would cause in such a medium some kind of diffraction or interference phenomena and that a crystal would provide such a medium. Although his colleagues Sommerfeld, W. Wien and others, with whom he discussed the idea on a skiing expedition, raised objections to the idea, W. Friedrich, one of Sommerfeld's assistants and P. Knipping tested it out experimentally and, after some failures, succeeded in proving it to be correct. Von Laue worked out the mathematical formulation of it and the discovery was published in 1912. It established the fact that X-rays are electromagnetic in nature and it opened the way to the later work of Sir William and Sir Lawrence Bragg. Subsequently von Laue made other contributions to this subject.

Also prominent in von Laue's work were his contributions to the problems of superconductivity which he made when he was Professor of Theoretical Physics at Berlin University. At this time Walther Meissner was studying at the Physikalisch-Technische Reichsanstalt in Berlin, the remarkable disappearance of ohmic resistance shown by many metals at temperatures of the order of that of liquid helium. An especially valuable contribution then made by von Laue was his explanation, in 1932, of the fact that the threshold of the applied magnetic field which destroys superconductivity varies with the shape of the body because, when the magnetic field is established after the state of superconductivity has been established, the magnetic field is deformed by the supercurrents induced at the surface of the metal being used. This explanation was confirmed and it opened the way to Meissner's subsequent discovery that a superconductor eliminates the whole magnetic field in its interior and this became the basic idea of F. and H. London's theory of superconductivity. Von Laue published one paper in collaboration with F. and H. London and between 1937 and 1947 he published a total of 12 papers and a book on this subject.

Among the many honours and distinctions which he was awarded were the Ladenburg Medal, the Max-Planck Medal and the Bimala-Churn-Law Gold Medal of the Indian Association at Calcutta. He held Honorary Doctorates of the Universities of Bonn, Stuttgart, Munich, Berlin, Manchester and Chicago, was a member of the Russian Academy and the Academy of Sciences of Berlin, the German Physical Society and Mathematical Society, the Kant Society, the Academy of Sciences of Vienna, the American Physical Society, the Soci?t? Fran?aise de Physique and the Soci?t? Fran?aise de Mineralogie et Crystallographie. He was also Honorary Senator of the MaxPlanck Society and Honorary Member of the German R?ntgen Society, and Corresponding Member of the Academies of Sciences of G?ttingen, Munich, Turin, Stockholm, Rome (Papal), Madrid, the Academia dei Lincei of Rome, and the Royal Society of London. In 1948 he became Honorary President of the International Union of Crystallographers, in 1952 he was made a Knight of the Order Pour le M?rite, in 1953 he received the Grand Cross with Star for Federal Services, and in 1957 he became an Officer of the Legion of Honour of France. Much esteemed by his contemporaries for his character and sound judgment, von Laue's opinions were often sought and during his life he exerted great influence on the direction and development of German scientific work. Among his characteristics were a deep love and admiration of Prussia and a strong sense of justice and fair play. When Hitler and the National Socialist Party were in power, he defended, even at the risk of reprimand or personal injury, scientific views, such as the theory of relativity, which were not approved by the Party or by such strong adherents to it as the physicist Lenard. When Einstein resigned from the Berlin Academy and the Vice-President of this Academy stated that this was no loss, von Laue was the only member of the Academy who protested.

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