Ernst Bessel Hagen

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(Carl) Ernst Bessel Hagen (born January 31, 1851 in Königsberg ; † January 15, 1923 in Solln near Munich ) was a German applied physicist and experimental physicist. Along with Heinrich Rubens , he developed the physical Hagen-Rubens relation bez. electrical conductivity of metals.

life and work

Ernst Bessel Hagen was the son of the Reichstag member and Berlin city treasurer Adolf Hermann Wilhelm Hagen . His grandfathers were the Königsberg professors for political economy Carl Heinrich Hagen and for astronomy Friedrich Wilhelm Bessel , a great-grandfather was Karl Gottfried Hagen . As a professor, his brother Fritz Karl Bessel-Hagen was the first chief surgeon at the Berlin-Charlottenburg City Hospital, while his brother Werner was a Prussian diplomat. He was married to Wilhelmine von Bezold, a daughter of the meteorologist Wilhelm von Bezold , with whom he had two sons.

Ernst Bessel Hagen studied mathematics, physics and chemistry at the universities of Berlin and Heidelberg after graduating from high school in Berlin's Luisenstädtisches Gymnasium in 1871 . In Heidelberg he was assistant to Robert Wilhelm Bunsen from 1873 to 1875 , with whom he received his doctorate in 1875. He then worked for two years as assistant to August Toepler at the Polytechnic in Dresden, whose mercury vacuum pump he later improved, and from 1878 to 1883 with Hermann von Helmholtz at the University of Berlin. In 1883 he completed his habilitation there on the thermal expansion of alkali metals and was then a private lecturer in physical observation methodology and later in physiological optics. In 1885 he attracted attention with a book on electric lighting in the USA, which he had studied on a trip the previous year, and was then often consulted by official bodies on such issues.

From 1884 to 1888 he was associate professor for applied physics and director of the newly founded electrotechnical laboratory at the Dresden Polytechnic . In 1887 he became senior electrical engineer and physicist with the Imperial Navy in Kiel and admiralty councilor. In 1893 he became director of the second department of the Physikalisch-Technische Reichsanstalt (PTR) founded six years earlier in Charlottenburg under its director Hermann von Helmholtz. He stayed there until his resignation in 1918, which was triggered on the one hand by health reasons, but he also did not agree with the changes in the PTR under the then director Emil Warburg .

From 1894 he was a member of the Imperial Standardization Commission and from 1895 to 1908 an extraordinary member of the Patent Office. He was also active on the board of the Deutsches Museum .

He received the title of a secret councilor .

From 1897 to 1908, together with Heinrich Rubens , he investigated the reflection and emission of electromagnetic radiation by metals and established relationships with their electrical conductivity, which ultimately led to the Hagen-Rubens relationship , which describes the relationship between optical reflection and electrical conductivity describes as an approximation in the infrared spectral range. Hagen was also involved in Rubens' extensive investigations into black body radiation . The experiments by Hagen and Rubens served to confirm Maxwell's electrodynamics, in particular the approach of a constant, frequency-independent conductivity up to the infrared frequency range.

literature

Individual evidence

  1. ↑ He published as Ernst Hagen .
  2. ↑ Annalen der Physik 1881
  3. ↑ Ernst Hagen: The electrical lighting - with special consideration of the systems predominantly used in the United States of North America for central systems , Springer Verlag 1885
  4. ↑ with Rubens: Relationship of the reflectivity and emissivity of metals to their electrical conductivity. Annals of Physics , Volume 9, 1903
  5. ^ Bergmann, Schaefer: Optics. De Gruyter, 2004, p. 279
  6. ↑ FEM Silveira, Kurcbart, SM: Hagen-Rubens relation beyond far-infrared region . In: EPL (Europhysics Letters) . 90, No. 4, May 1, 2010, p. 44004. doi : 10.1209 / 0295-5075 / 90/44004 . Retrieved April 15, 2013.
  7. ↑ with Rubens: Change in the emissivity of metals with temperature in the short-wave ultra-red spectrum. Meeting reports of the Royal Prussian Academy of Sciences, Volume 23, 1910
  8. ↑ with Rubens: About the dependence of the emissivity of metals on the temperature. Meeting reports of the Royal Prussian Academy of Sciences, Volume 16, 1909
personal data
SURNAME Hagen, Ernst Bessel
BRIEF DESCRIPTION German physicist
DATE OF BIRTH January 31, 1851
PLACE OF BIRTH Königsberg , Kingdom of Prussia
DATE OF DEATH January 15, 1923
Place of death Solln , Bavaria