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Sir Joseph John Thomson (1856-1940). Portrait of Sir Joseph John Thomson, English physicist and discoverer of the electron. Thomson was born near Manchester. In 1876 he entered Cambridge University, and remained there for the rest of his life. Expanding on previous work with cathode rays, he showed that they may be deflected by an electrical field. He was also able to measure their mass to charge ratio, deducing that they were particles much smaller than an atom. For this proof of the existence of the electron, he was awarded the 1906 Nobel Prize for Physics, and was knighted in 1908. He later demonstrated the existence of isotopes before his death in 1940.
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