Becquerel's phosphoroscope

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The Becquerel Phosphoroscope ( Alexandre Edmond Becquerel ) is a device to measure the phosphorescence of z. B. to measure ruby ​​or glass. The construction was later improved by Philipp Lenard .

The specimen is exposed briefly and intensively in a periodic sequence in such a device. The device consists of a light source with a lens system to focus the light beam and a motor that rotates a disk. In the disk there are longer and shorter holes in a skilful order which, during rotation, allow the bundled light beam to fall onto the specimen behind. In this way, the specimen is intensively illuminated at short intervals in the same period.

After the illumination, radiation in the form of light is emitted from the specimen for a very short period of time (usually a few milliseconds ). This process is called phosphorescence or more generally luminescence .

With a second, rotating disk, which is located behind the specimen, and the holes of which are exactly offset from the front disk, it is possible to measure the radiation emanating from the specimen using a photomultiplier. While the specimen is being illuminated, no light may reach the rear, as otherwise the photomultiplier would be exposed too much - hence the offset holes. The photocurrent generated in the photomultiplier is used to control the movement of the light point of an oscilloscope. The half-life time (time up to half of the start intensity) and the relaxation time (decay time) can now be measured on the oscilloscope screen.

literature

  • Otto Lueger : Lexicon of the entire technology and its auxiliary sciences . 2nd Edition. Deutsche Verlagsanstalt, Stuttgart and Leipzig 1920 ( zeno.org [accessed September 24, 2019] Lexicon entry “Phosphoroskop”).
  • Meyer's Large Conversation Lexicon . 6th edition. Bibliographisches Institut, Leipzig / Vienna 1909 ( zeno.org [accessed on October 8, 2018] lexicon entry "Phosphorescence").