"Untuk kerjanya dalam sinar katode".
|Philipp Lenard (eng) |
Lénárd Fülöp (hu)
Philipp Lenard in 1900
|Born||June 7, 1862(1862-06-07) |
Pozsony, Kingdom of Hungary, Austrian Empire
|Died||May 20, 1947(1947-05-20) (aged 84) |
|Citizenship||Hungarian in Austria-Hungary (1862-1907), |
|Institutions||University of Budapest |
University of Breslau
University of Aachen
University of Heidelberg
University of Kiel
|Alma mater||University of Heidelberg|
|Doctoral advisor||Robert Bunsen|
|Known for||Cathode rays|
|Notable awards||Nobel Prize for Physics (1905)|
On Cathode Rays
Award Ceremony Speech
As the cathode rays reached Lenard's "aluminium window", it was found that they passed through it and continued their course in the air outside the tube. This constituted a discovery which was to have the most far-reaching consequences, above all for the study of the radiation phenomena themselves. It became possible to study cathode rays under much simpler and more convenient experimental conditions than before, and also to separate observations on conditions needed for the production of the rays in the tube from questions concerning their propagation and other characteristics.
It was also discovered that these rays pass unimpeded through empty space but that in gases they are subject to diffusion which increases with the density of the gas; and, moreover, that bodies in general differ in permeability, as their absorptive power bears a direct relationship to their density. Cathode rays proved to be carriers of negative electricity even in empty space and they could be deflected from their path by both magnetic and electrical fields.
Finally, Lenard showed that there are various types of cathode rays, differentiated amongst other things by the fact that they are deflected by magnets, to a greater or lesser extent. He also found that the formation of one or other type of ray is determined by the degree of gas rarification in the discharge tube.
Since then, however, this theory has had to be modified in several significant details in order to reconcile it with phenomena which have been brought to light through the work of Lenard and others. It was shown, for example, that these particles which, according to Crookes, are ejected from the cathode - the so-called "electrons" - must have a considerably smaller mass than chemical atoms, that the velocity of these electrons can come to about one-third of the speed of light, but that there are also cathode rays which are considerably slower: the various types of cathode rays are in fact explained by the different speeds with which they are ejected from the cathode.
In his more recent work Lenard has been able to produce cathode rays with relatively slow speed, rays which are formed through the influence of ultraviolet light on bodies charged with negative electricity. This has also served to explain an important phenomenon noted by other research workers.
The study of electrons, their characteristics and their behaviour in relation to matter has been given a sounder basis through these researches on cathode rays and has been gradually developed into one of the foremost theories of modern physics by Lenard himself and by other workers.
This theory is in fact not only important for the explanation of cathode rays and other closely related phenomena - the electron theory with its concepts on the constitution of matter has become of the most fundamental importance for the sciences of electricity and of light and for both the physicist and the chemist.
It gave an impetus to the search for other thus far unknown sources of similar rays, and the revolutionary discoveries by past Nobel Prize winners - Röntgen, Becquerel and the two Curies - and by other scientists which have followed can well be considered the fruits of this impetus and links in the history of development of one and the same science.
Nobel Prize Org.
Disusun Ulang Oleh;
Pendidikan Fisika, FPMIPA. Universitas Pendidikan Indonesia
Follower Open Course Ware at MIT-Harvard University, Cambridge. USA.
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