J J Thomson with his son and daughter, c 1909

J J Thomson with his son and daughter, c 1909. One of a set of five framed photographs of Sir Joseph John Thomson (1856-1940). Thomson 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 that these rays were particles, but German physicists maintained that they were a type of electromagnetic radiation. Thomson showed that cathode rays were particles much smaller than the atom with a negative charge. These particles were later renamed electrons. In 1906 he was awarded the Nobel Prize for Physics for his research on conduction through gases. In 1912 he went on to develop mass spectrometry (the study of the structure and properties of molecules and compounds). ©SSPL/Science Museum