Leonard (Lenard), Philipp von( German physicist, Nobel Prize in Physics, 1905)
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Biography Leonard (Lenard), Philipp von
June 7, 1862, Mr.. - May 20, 1947
German physicist Philipp Eduard Anton von Lenard was born in Pressburg in Austria-Hungary (now Bratislava, Czecho-Slovakia) and was the only child of a wealthy wine merchant Philip von Lenard and Antonia nee Bauman. When L. was very young, his mother died, and was brought up by his aunt. She subsequently married the father L. Up to nine years, L. studied at home, and then to the school at the cathedral and pressburgskoy High School. His favorite subjects were mathematics and physics. School course, he adds: reading university textbooks, conducted physical and chemical experiments.
Despite the interest L. the natural sciences, his father insisted that he inherited the wine trading business. He wanted a son enrolled at the Technical University of Vienna and Budapest, where he could study chemistry - the subject of particular importance for wine. In 1882, Mr.. L. reluctantly began to work in the company of his father. A year later he was on their own savings to Germany, where he attended lectures of the famous chemist Robert Wilhelm Bunsen (inventor Bunsen burner). This trip further reinforced his intention to become a scientist. Winter 1883. L. enrolled in the University of Heidelberg, where he studied physics. L. spent four semesters at Heidelberg and two in the University of Berlin, where he worked under the guidance of such renowned scholars as Bunsen and the physicist and physiologist Hermann von Helmholtz. In 1886. in Heidelberg, he defended his thesis, for which he was awarded a doctoral degree summa cum laude. The work was devoted to the fluctuations of water drops. Within three years after the protection L. worked as an assistant in Heidelberg, the German physicist Georg Quincke.
While studying at the university during the holidays A. with his high school physics teacher Virgil Klatten conducted studies of phosphorescence. They found that some phosphorescent materials only if they contain traces of certain metals. Being engaged in other studies, L. continued to explore the phosphorescence for more than forty years.
Leaving Heidelberg, L. within a short time worked in London and Breslau (now Wroclaw, Poland), and in April 1891. became assistant to Heinrich Hertz in Bonn University. Hertz, . gain prominence experimental discovery of electromagnetic radiation, . whose existence was predicted by James Clerk Maxwell, . accidentally discovered the photoelectric effect (emission of electrically charged particles surface, . which the incident radiation, . in this case, ultraviolet),
. One of the phenomena that are particularly interested in Hertz, were cathode rays, revenue pumped well discharge glass tube from the negative electrode (cathode) to the opposite end of the tube. Their study involved many scientists, among which the most noteworthy of the English physicist William Crookes. Mystery of cathode rays attracted the attention of A. in 1880, when he read an article Crookes 'radiant matter, or the fourth physical condition' ( "Padiant Matter, or the Fourth Physical State").
Hertz and L. decided to investigate the cathode rays in a more comfortable environment - without flash tube. Since Hertz discovered that cathode rays pass through a thin aluminum foil, L. manufactured glass discharge tube with a small hole at the anode (positive electrode), a closed foil (such openings later became known as the windows Lenard). Placing on the path of cathode rays instead of the usual second air discharge tube, L. managed to get a longer light beam, part of which was isolated from the source and more convenient for experimentation. Deflecting the beam electric and magnetic fields, h. showed that cathode rays consist of negatively charged particles. He was able to measure the ratio of charge of these particles to their mass. Initially, the same L. considered cathode rays intangible radiation. He also found, . that these particles penetrate into the air and other substances at various depths, . and the absorption approximately in proportion to the thickness and density of the absorbing substance, and that the rays, . emitted by gas discharge tubes, . at high voltages, . corresponding to greater speed and energy of the particles, . have a higher penetration ability.,
. The study of cathode rays L
. worked for twelve years. After the death of Hertz in 1894, Mr.. L. for a short time became acting director of the Physics Institute of Bonn University. A year or two, he taught at the universities of Breslau, Aachen and Heidelberg. Then he became a professor and became director of the physical laboratory at the University of Kiel (1898). Despite the recognition, which got its work, L. sometimes with disdain and envy belonged to the success of other scientists. It is with the greatest respect for the Hertz, but, as his assistant in Bonn, is sometimes thought that he treats them respectfully enough.
When in 1895. Wilhelm Roentgen discovered the rays, bearing his name now (and arising in the bombardment of cathode rays parts of the discharge tube), L. was depressed by the fact that he was not found them first. Subsequently, he always called them 'high-frequency radiation', but never used them universally accepted names of 'X-rays' or 'X-rays'. Moreover, L. believed that borrowed Roentgen discharge tube, it is in the discovery of new radiation contributed deserving special mention. Once in 1897. Dzh.Dzh. Thomson discovered the electron and its opening has been widely recognized, L. argued that the priority allegedly belonged to him. Thomson gave a quite modern description of the electron, and h. same in 1906. continued to call the electron 'electricity without matter, electric charge without charged bodies', spoke about 'electricity in its pure form'.
One of the major scientific achievements L. was produced by him in 1902. experimental observation, . according to which a free electron (he called it a cathode ray) must possess a certain minimum energy to, . to ionize the gas (to make a neutral gas of electrically charged) by knocking a bound electron from an atom,
. L. called secondary electrons knocked atomic cathode rays. He gave a very accurate estimate of the ionization potential (energy required for ejection of an electron) for hydrogen.
In the same 1902. L. proved, . that the photoelectric effect produces the same electrons, . are found in cathode rays, . photoelectrons and not simply released from the metal surface, . a fly with a certain energy (velocity) and that the number of electrons emitted from the metal increases with the intensity, . but the speed of the electrons never exceeds certain limit,
. These experimental data were explained in the work of Albert Einstein (1905), which is used for the quantum theory of Max Planck. According to Einstein, light consists of tiny, discrete clusters of energy, later called photons received. The photon energy is proportional to the frequency of light.
In the photoelectric effect each photon transfers its energy to an electron in the irradiated surface of the metal, in principle, allowing the electrons 'fly' from the metal. The more intense the light, the more photons and electrons is pulled out, but a fixed photon energy sets a limit to the speed of each electron.
In 1903, Mr.. L. hypothesized that the atom is mostly empty space. That is the conclusion he had come, watching as the electrons pass through the window Lenard and penetrate through the air and other substances. L. suggested that the positive and negative electrical charges in the atom (the number of which must be equal, to ensure its electrical neutrality) are found closely associated in pairs, which he called dinamidami. Concept A. was interesting and represented a significant step forward compared with earlier views. But she was wrong, as was demonstrated in eight years, Ernest Rutherford proposed the model of the atom, in which around a very dense positively charged nucleus at a relatively great distance from him turn negatively charged electrons.
. Although L
. repeatedly was very close to that to make discoveries that have brought well-deserved recognition of other. Nobel Prize 1905. was awarded to him 'for his work on cathode rays'. At the award ceremony Arne Lindstedt from the Royal Swedish Academy of Sciences said: 'It is clear that the work of L. on cathode rays, not only enriched our knowledge of these phenomena, but in many ways laid the foundation of the theory of electrons'.
In 1907, Mr.. L. Quincke's successor as Professor of Experimental Physics, University of Heidelberg. In 1909, Mr.. He took over more and Acting Director of the newly established Institute for Radiological Sciences in Heidelberg. The most important work done under his leadership in this institute, was associated with a spectral analysis of light emitted by excited atoms and molecules.
Reputation L. in some academic circles in Germany was still quite high, but it started to fall. Made A. in 1910. report on the air, penetrating the space - an idea strongly discredited by the time - Einstein described as 'infantile'. In addition, since the beginning of World War L. became an ardent nationalist, and has repeatedly attacked the British, accusing them of misappropriating the achievements of German scholars. After the defeat of Germany, he spoke disparagingly of the Weimar Republic, because she 'resigned in disgrace in Germany', and incited the students to fight against the regime. L. was among those who initially supported Adolf Hitler and became an anti-Semite.
L. was inherent natural tendency to experimental studies, which he called 'pragmatic truly Germanic physics', and he abhorred physical theories with complex mathematical apparatus. Such theories L. called 'dogmatic Jewish physics'. Particular hostility he expressed towards Einstein, with sharp attacks on that ( 'with undisguised anti-Semitic taint', in the words of Max Born), made at a scientific congress in 1920,. Overestimated he even scientific heritage Hertz, dividing it into a good experiment and a bad theory, attributing the recent Jewish origin scientist. After the Nazis came to power in 1933. L. received the title of head of the Aryan, or Germanic, physics and became a personal adviser to Hitler. He explained Fuhrer its own version of physics with the racist orientation. In 1897. L. married Katharine Shlener. Leaving Heidelberg in 1945, he settled in the village Messelhauzen, where he died two years later. Most scholars denounced the ideological preferences LA, which marred the clarity of his judgments about the physics in later years. Carl Ramsauer, disciple and colleague L. for over thirteen years, called it 'tragic figure'. He observed that 'his achievements were of paramount importance, and yet his name was not closely or intimately associated with any one of the milestones in the development of physics'.
In addition to the Nobel Prize, A. won many awards, including medals Franklinovskogo Franklin Institute and honorary doctorate from University Christian (now Oslo), Dresden and Pressburg. In 1933. He was awarded the 'Third Reich' Order of the Eagle.