William crookes (1832-1919)

Crookes was a British physicist and chemist. In 1861, he discovered the element thallium.
His studies on electrical discharges in vacuum tubes resulted in the Crookes tube, an early cathode ray tube,
in 1880 he found that 'cathode rays' cast shadows and traveled in straight lines, which could be deflected by a magnet.
He believed that cathode rays were made up of negatively charged particles (electrons).


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