Signed photograph of Sir William Lawrence Bragg (1890-1971). In 1921 Bragg, together with his father Sir William Henry Bragg (1862-1942), was the first to show that molecular structure could be deduced from the pattern of diffraction of X-rays by a crystal sample. Father and son worked together, jointly winning the Nobel prize for physics in 1915. Bragg headed the Cavendish Laboratory in Cambridge (1938-1953) supporting James Watson (b 1928) and Francis Crick (b 1916) in their pioneering work, deducing the helical structure of DNA using X-ray crystal studies. Bragg became director of the Royal Institution (1954-1965) as did his father before him. They also invented an X-ray spectrometer together.
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