Sir Joseph J Thomson (1856-1940) with his apparatus. JJ Thomson was the son of bookseller who studied sciences at Trinity College, Cambridge. After graduating, he continued to work at Cambridge University and in 1896 began experiments on cathode rays. In Britain physicists argued these rays were particles, but German physicists maintained they were a type of electromagnetic radiation. Thomson showed that cathode rays were particles with a negative charge and much smaller than an atom. These particles were later renamed electrons. In 1912 he went on to develop mas spectrometry. In 1906, he was awarded the Nobel Prize for Physics, for research on conduction through gases.
© Science Museum / Science & Society Picture Library