Lummer, Otto

Lummer studied at various German universities, and in 1884, after completing his dissertation, became Hermann von Helmholtz 's assistant at Berlin University . In 1887, Lummer followed Helmholtz to the newly created Institute of Physics and Technology ( Physikalisch-Technische Reichsanstalt ), where he first served as an assistant, from 1889 as a research assistant, and in 1894 received the title of professor. Since 1901, Lummer also taught at the University of Berlin as a private assistant professor , and in 1904 received a professorship at the University of Breslau (now Polish Wroclaw ). In 1924, at the initiative of Lummer, the Schlesische Funkstunde radio station was founded in Breslau; The scientist became its co-founder and first chairman of the board.

Optics

In 1884, in his dissertation, Lummer rediscovered bands of equal slope ( English Haidinger fringe ), arising from the interference of light in plane-parallel glass plates and discovered for the first time by Wilhelm Heidinger . In 1901, Lummer used the idea of ​​interference of light beams repeatedly reflected inside a plane-parallel plate to create a high-resolution spectrometer . The following year, Ernst Gercke added an input prism to the device to reduce radiation losses. An improved device in this way is called a Lummer – Gehrcke interferometer plate, or interferometer .

From the moment of its foundation, the employees of the Physicotechnical Institute had the task of creating standards for determining illumination and other photometric quantities. To solve this problem, a number of new devices have been created. In 1889, Lummer, together with Eugen Brodhun ( English Eugen Brodhun ) invented the photometric cube, also known as the Lummer - Broadhun photometer ; In terms of sensitivity, this device was more than two times superior to the standard for that time aperture photometer invented by Robert Bunsen . In 1892, together with Ferdinand Kurlbaum, Lummer improved the bolometer scheme proposed by Samuel Langley , and achieved not only an increase in its sensitivity (temperature changes of the order of 10 ⁻⁷ ° C) and speed (inertia of about 8 s), but also the ability to compare two sources radiation, simultaneously illuminating the device from two sides. To create such a device (a “large-area bolometer”), an original technology was developed to create thin blackened platinum wires, which was also used to implement the so-called linear bolometer in 1899. These bolometers, as well as the spectrobolometer, which is a modification of the spectrometer for operation in the infrared range , were used in subsequent measurements of the radiation intensity in the blackbody spectrum.

In 1902, Lummer created the production of mercury vapor lamps as sources of monochromatic light .

Blackbody Radiation

In 1895, together with Wilhelm Vinh, Lummer proposed a method for realizing a completely black body using a blackened cavity with a small hole; The radiation emerging from this cavity heated to a certain temperature is the desired equilibrium thermal radiation. The following year, Lummer substantiated this method in detail, noting that the emitters used earlier (for example, blackened metal plates) were not black enough and could not ensure the accuracy of determining the properties of a black body. In addition to interest in fundamental physical laws, the motivation for creating an artificial absolutely black body was the need for a standard of absolute radiation intensity . In 1897/98, Lummer, with the help of his collaborator Ernst Pringsheim, completed the practical implementation of the black body: it was a spherical or cylindrical metal cavity (iron and copper were used), which was covered on the inside with soot or uranium oxide; To stabilize the temperature, the cavity was placed in various liquids (liquid air, boiling water, hot saltpeter, etc.) or in a clay oven. This method made it possible to obtain equilibrium radiation in the temperature range from -188 ° to +1200 ° C. Thus, advances in experimental technology have allowed researchers to begin reliable measurements of black body characteristics. In 1897, Lummer and Pringsheim checked the Stefan-Boltzmann law , and later found the numerical value of the constant equal to the product of the wavelength corresponding to the maximum of the spectrum and temperature, and, therefore, confirmed the Wien displacement law . To achieve even higher temperatures, in 1898 they developed a black body with electric heating: the porcelain cavity blackened inside was placed in a platinum cylinder to which electrical contacts were connected; this system was isolated from external influences by several layers of heat-resistant material. Using this scheme, experimenters were able to raise the temperature of the black body to 1500 ° C, and in 1903 they brought it to 2100 ° C, using a graphite tube placed in a gas atmosphere instead of platinum. This design of a completely black body is still used in experimental studies.

On February 3, 1899, at a meeting of the German Physical Society, Lummer and Pringsheim presented the first results of their measurements of the energy distribution in the spectrum of an absolute black body (in the wavelength range from 0.2 to 6 μm and at temperatures of 800–1400 ° C). In general, their data were consistent with the Wien radiation law, which was theoretically derived in 1896. In the following months, experimenters improved their techniques to expand measurements into the long-wavelength region. On November 3, 1899, Lummer reported on the presence of systematic deviations of the experiment from theory, but the situation remained unclear, since measurements taken at about the same time by Friedrich Paschen did not reveal any deviations from Wien's law. At a meeting on February 2, 1900, Pringsheim presented new results of his measurements with Lummer, confirming the presence of deviations from Wien's law, especially in the long-wavelength region (their experiments covered wavelengths up to 18 μm). Thus, the validity of the Wien radiation law was called into question. Soon, Lummer, together with Eugen Jahnke of Germany ( German: Eugen Jahnke ) proposed a generalization of this law, so that in the region of long waves the intensity of thermal radiation became proportional to temperature. This was experimentally confirmed by Heinrich Rubens and Kurlbaum, who measured the blackbody spectrum up to a wavelength of 51.2 microns. These fundamental studies of the energy distribution in the spectrum of a black body created the prerequisites for Max Planck's derivation of his famous formula and the creation of a further quantum theory of thermal radiation.

• Lummer O. Über eine neue Interferenzerscheinung an planparallelen Glasplatten und eine Methode, die Planparallelität solcher Gläser zu prüfen // Annalen der Physik . - 1884. - Bd. 259 (23). - S. 49-84.
• Lummer O., Brodhun E. Photometrische Untersuchungen // Zeitschrift für Instrumentenkunde. - 1889. - Bd. 9. - S. 41-50, 461-465.
• Lummer O., Kurlbaum F. Bolometrische Untersuchungen // Annalen der Physik. - 1892. - Bd. 282 (46). - S. 204-224.
• Wien W., Lummer O. Methode zur Prüfung des Strahlungsgesetzes absolut schwarzer Körper // Annalen der Physik. - 1895. - Bd. 292 (56). - S. 451-456.
• Lummer O., Pringsheim E. Die Strahlung eines “schwarzen” Körpers zwischen 100 und 1300 ° C // Annalen der Physik. - 1897. - Bd. 299 (63). - S. 395-410.
• Lummer O., Pringsheim E. Die Verteilung der Energie im Spektrum des schwarzen Körpers // Verhandlungen der Deutschen Physikalischen Gesellschaft. - 1899. - Bd. 1. - S. 23–41.
• Lummer O., Pringsheim E. Über die Strahlung des schwarzen Körpers für lange Wellen // Verhandlungen der Deutschen Physikalischen Gesellschaft. - 1900. - Bd. 2. - S. 163-180.
• Lummer O., Jahnke E. Über die Spectralgleichung des schwarzen Körpers und des blanken Platins // Annalen der Physik. - 1900. - Bd. 308 (3). - S. 283-297.
• Lummer O., Gehrcke E. Über die Anwendung der Interferenzen an planparallelen Platten zur Analyse feinster Spektrallinien // Annalen der Physik. - 1903. - Bd. 315 (10). - S. 457-477.
• Lummer O., Reiche F. Die Lehre von der Bildentstehung im Mikroskop von Ernst Abbe. - Braunschweig, 1910.
• Lummer O. Grundlagen, Ziele und Grenzen der Leuchttechnik. - München, 1918.
• Eucken A. (Hrsg.), Lummer O. (Hrsg.), Waetzmann E. (Hrsg.). Müller-Pouillets Lehrbuch der Physik (11. Auflage). Zweiter Band: Lehre von der strahlenden Energie (Optik). - Braunschweig: Vieweg, 1926.

• Hermann A. Otto Richard Lummer // Dictionary of Scientific Biography. - New York: Charles Sribner's Sons, 1973. - Vol. 8. - P. 551–552.
• Temples Yu. A. Lummer Otto Richard (Lummer Otto Richard) // Physicists: Biographical Reference / Ed. A.I. Akhiezer . - Ed. 2nd, rev. and add. - M .: Nauka , 1983 .-- S. 173. - 400 p. - 200,000 copies. (per.)
• Jemmer M. The evolution of the concepts of quantum mechanics. - M .: Science, 1985.
• Mehra J. Max Planck and the law of blackbody radiation // Mehra J. The golden age of theoretical physics. - 2001. - P. 34-37.
• Hoffmann D. On the Experimental Context of Planck's Foundation of Quantum Theory // Centaurus. - 2001. - Vol. 43. - P. 240—259.
• Huebener RP, Lübbig H. The Optical Laboratory and the Birth of Quantum Theory // A Focus Of Discoveries. - World Scientific, 2008. - P. 47-60.

• Otto Lummer Pupils of Otto Lummer . North Dakota State University. Date of treatment August 27, 2012. Archived October 29, 2012.