The scientific background

The discovery of x-ray diffraction and the work of the Braggs 1909-1915

Setting the scene

William Henry Bragg (WHB) (1862-1942) was appointed Cavendish Professor of Physics at the University in 1908. Following the discovery of X-rays by Wilhelm Röntgen in 1895 and radioactivity in uranium by Henri Becquerel in 1896, Bragg had studied, whilst at the University of Adelaide, radioactive emission, the ionisation of gases and the nature of X-rays - which he held to be 'corpuscular' rather than wave-like in nature.

His earliest years at Leeds (from 1909) were not entirely happy ones. The lack of resources, the poverty and grime of smoky Leeds (as compared with sunny Adelaide), the inattentive students, his feeling of social and scientific isolation (the corpuscular theory of X-rays and γ-rays was giving ground to the wave theory) - depressed his spirits. However, his confidence was upheld through the support of Arthur Smithells, Professor of Chemistry, his correspondence with Ernest Rutherford in Manchester and not least the clearly emerging scientific abilities of his elder son, Lawrence.

William Lawrence Bragg (WLB) (1890-1971) had already achieved a first-class degree at the University of Adelaide before coming to England. He enrolled at Trinity College, Cambridge, first to read mathematics but then switched (perhaps on his father's advice) to natural sciences. One teacher was C T R Wilson, whose lectures in optics, interference and diffraction phenomena were to have, as WLB himself records, a seminal influence on him. WLB graduated, again with a first class degree in 1912 and immediately began research in the Cavendish laboratory, under the supervision of Professor J J Thomson.

It was a hopeless time for him; there was very little apparatus available, virtually no workshop facilities and he made no progress with his research project (on ionic mobility) at all. However, all this was shortly to change. In order, perhaps, to escape for a time from the frustrations of the Cavendish Laboratory, in August 1912, he joined his family for a holiday at Cloughton - a village between Scarborough and Robin Hood's Bay on the Yorkshire coast - and it was here that he heard from his father the first news of Max Laue's discovery, at the University of Munich, of the scattering of X-rays by crystals.