1877-1944

English physicist noted for his research and important discoveries concerning x-rays. He was awarded the 1917 Nobel Prize for Physics for discovering that x-ray scattering depends on the molecular weight of gases through which it passes (1903). In 1904 Barkla observed x-ray polarization, which suggested x-rays were a form of electromagnetic radiation. He also noted that secondary radiation produced by x-ray absorption was of two types—later referred to as K-radiation and L-radiation.