Sir William Henry Bragg (1862-1942), the English physicist. In 1909 he took up duties as professor at Leeds and there began work on X-rays. In 1913 Bragg found that when X-rays are generated by the impact of high-energy electrons on a platinum target. then as well as a continuous spectrum of X- rays, there is also some X-ray lines whose position is characteristic of the metal target. Moseley was shortly to use these X-ray spectra in a valuable way. Bragg, with his son Lawrence, went on to examine the wavelengths of X-rays by using crystals; their method founded X-ray crystallography. Bragg and his son won the 1915 Nobel prize for physics.