The only son of the noted physicist Sir J.J. Thomson, he worked in the Cavendish Laboratory at Cambridge University after World War I. In 1922 he was appointed professor of natural philosophy at the University of Aberdeen, Scot., where he conducted experiments demonstrating that a beam of electrons is diffracted upon passage through a crystalline substance, thus confirming Louis de Broglie's prediction that particles should display the properties of waves that have a wavelength (λ) equal to the ratio of the Planck constant (h) to the momentum (p) of the particle; that is, λ = h/p.

In 1930 Thomson became professor of physics at the Imperial College of Science in London; there he concentrated on studies of the neutron and nuclear fusion. He was knighted in 1943 and nine years later became master of Corpus Christi College, Cambridge, from which he retired in 1962. His works include Theory and Practice of Electron Diffraction (1939) and J.J. Thomson and the Cavendish Laboratory in His Day (1965).