Ueber die lichtelektrische Wirkung. Also Einstein's Ueber die thermodynamische Theorie der Potentialdifferenz..

Leipzig, 1902. Lenard, Philipp (1862-1947). Ueber die lichtelektrische Wirkung. In Annalen der Physique , 4th ser., 8 (1902): 149-198. Plate. [With:] Einstein, Albert (1879-1955). Ueber die thermodynamische Theorie der Potentialdifferenz zwischen Metallen und vollstandig dissociierten Losungen ihrer Salze und uber eine elektrische Methode zur Erforschung der Molecularkrafte. In ibid.: 798-814. Whole volume, 8vo. viii, 928pp. 7 plates. 211 x 140 mm. Early 20th cent. cloth, spine faded, slight wear. Very good copy.

First Editions. Lenard's paper on the photoelectric effect contains a crucial discovery: "as the intensity of the light increases the number of electrons set free rises, but their velocity remains unaffected: the velocity depends solely on wavelength" (DSB). This observation became an integral part of Einstein's hypothesis of light quanta, published in the Annalen der Physique in 1905; see Pais, pp. 380-81.

In the same year, Lenard received the Nobel Prize in physics for his cathode ray studies, particularly his use of the "Lenard window," a device that allowed the rays to be studied independently of the discharge process. Lenard's work in this area represents "an indispensable step in the development of modern physics" (Magill, p. 89).

This volume of the Annalen der Physique also contains Einstein's 1902 paper on the thermodynamics of electrolysis, in which he was seeking experimental support for his incorrect hypothesis concerning molecular forces; see Pais, pp. 56-57. Also included in the volume are papers by Ferdinand Braun, Johannes Stark and Wilhelm Wien, all recipients of the Nobel Prize for physics. Pais, Subtle is the Lord, pp. 56-57; 380-81. Magill, The Nobel Prize Winners: Physics, I, 87-95.

.