Karl Heinrich Wiederkehr: Photoeffekte, Einsteins Lichtquanten und die Geschichte ihrer Akzeptanz

Zum 125 jŠhrigen Geburtstag Albert Einsteins

 

It is generally supposed, that the discovery of the efficacy-quantum by Planck was the impetus to EinsteinÕs hypothesis of lightquanta. With its help Einstein could explain the external light-electrical effect. But even years before Einstein had worked at the photoeffect and already made experiments on it. For that reason the article gives a short survey about the history of the lightelectric effects. LenardÕs basical work about the release of the photoelectrons is dealt with in detail, without which Einstein would scarcely have found his lightquanta. Furthermore it is shown how difficult it was for the physicists to give up – at least partially – the traditional view of the undulation-nature of light, and how they searched to explain the great energies of the photoelectrons. On the other side it is set forth how EinsteinÕs formula of lightquanta was gradually confirmed. The tragical development of EinsteinÕs personal relations with Johannes Stark and Philipp Lenard are briefly described. Stark was one of the few who supported EinsteinÕs ideas at the beginning. Only with the Compton-effect, which could only be quantitatively interpreted by means of lightquanta and the special theory of relativity 1923, the way was free for the general acceptance of the lightquanta. Einstein did not agree to the obtained dualism of undulation and corpuscle; he had a different solution in mind about the fusion of the two forms of appearance of light.

 

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