Bunsen-Roscoe Law

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The Bunsen-Roscoe law is the anti-proportionality, sometimes called the reciprocity law , between light intensity I and the exposure time t for a constant photochemical effect.

It is named after the chemists Robert Wilhelm Bunsen and Henry Enfield Roscoe , who quantitatively examined the blackening of photographic plates in 1862 and were able to use the data to prove that a constant exposure I · t is necessary for the same blackening . Qualitatively, however, the connection was already known from the time of the daguerreotypes , which had to be exposed for minutes even in sunshine.

In principle, the law also applies to damage to human skin.

Later deviations were discovered with very long and very short exposure times, see Schwarzschild effect or short-term effect . For example, the Bunsen-Roscoe law does not apply in biological systems because counter-regulations take place there that completely compensate for the effects of irradiation with a low dose rate. The proportionality is also not fulfilled in many photochemical processes, since the photochemical process is partly different in its first stages. For example, the law does not apply to photographic silver bromide gelatin layers or to larger fluctuations in intensity.

Individual evidence

  1. ↑ a b G. Kortüm: Colorimetry · Photometry and Spectrometry A guide for carrying out absorption, emission, fluorescence, scattering, turbidity and reflection measurements . Springer-Verlag, 2013, ISBN 978-3-642-87211-2 , p. 424 ( limited preview in Google Book search).
  2. ^ Robert Bunsen, Henry Roscoe: Photochemical investigations . VI. Treatise. Meteorological light measurements. In: Johann Christian Poggendorff (Ed.): Annals of Physics and Chemistry . 193 (Pogg. Ann. 117), no. 12 . Johann Ambrosius Barth, Leipzig 1863, p. 529–562 , doi : 10.1002 / andp.18631931202 ( online at Gallica , Bibliothèque nationale de France, page 538): "that within very wide limits the same products of light intensity and duration of insulation correspond to the same blackening on chlorine silver paper with the same sensitivity."
  3. ^ William Maddock Bayliss, L. Maass, EJ Lesser: Outline of General Physiology . Springer-Verlag, 2013, ISBN 978-3-662-42972-3 , p. 669 ( limited preview in Google Book search).
  4. ↑ G. Stüttgen, H. Schaefer: Functional Dermatology Basics of Morphokinetics Pathophysiology, Pharmacoanalysis and Therapy of Dermatoses . Springer-Verlag, 2013, ISBN 978-3-642-93018-8 , pp. 378 ( limited preview in Google Book search).
  5. ^ W. Waidelich, P. Kiefhaber: Laser / Optoelectronics in Medicine / Laser / Optoelectronics in Medicine Lectures of the 7th International Congress Laser 85 Optoelectronics Mit / Proceedings of the 7th International Congress with 2nd International Nd: YAG Laser Conference . Springer Science & Business Media, 2012, ISBN 978-3-642-70850-3 , p. 140 ( limited preview in Google Book search).
  6. ^ W. Bothe, J. Franck, P. Jordan, H. Kulenkampff, R. Ladenburg, W. Noddack, W. Pauli, P. Pringsheim, H. Geiger: Quanten . Springer-Verlag, 2013, ISBN 978-3-642-99593-4 , pp. 607 ( limited preview in Google Book search).
  7. ^ Walter Meidinger: Theoretical foundations of the photographic processes . Springer-Verlag, 2013, ISBN 978-3-662-41368-5 , pp. 288 ( limited preview in Google Book search).