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The First Vacuum Tube

The Nature of Cathode Rays

With a current passing the tube, a changing pattern of colorful lights emerges as it is evacuated. Research with the tube gave evidence that rays of some kind are traversing the tube. Thomson concluded that irrespective of the type of material at the cathode where the rays start the rays were the same.

The cathode rays are deflected by electric or magnetic fields, which show that they are electrically charged. By adjusting the relative strengths of the electric and magnetic forces surrounding a tube through which the rays were passing, Thomson was able to work out the mass per unit of charge of whatever particles the rays consisted of. He found that these entities were some 2000 times lighter than the lightest known atom, hydrogen. Moreover, the results were the same, independent of what metal the cathode in his tune consisted of, or what gas had been in the tube. He made the inspired guess that these "electrons" are constituents of hydrogen, and indeed of all elements.

When cathode rays in a vacuum are focused onto hard targets they can produce X-rays. Philipp E. A. von Lenard showed that cathode rays pass through thin leaves of metal, and thereby invented a cathode ray tube with a thin aluminum window through which the rays could pass into the open air.


Related Laureates

See also...

 The Nobel Prize in Physics 1905 - Philipp Eduard Anton von Lenard »  The Nobel Prize in Physics 1906 - Sir Joseph John Thomson  » X-rays  »

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