Andrew Lang, Emeritus Professor of Physics at the University of Bristol, has died. Born in 1924 at St Annes-on-Sea in the UK, Professor Lang obtained a First-Class Honours London External BSc in Physics at Exeter in 1944, a London External MSc in 1947 and a Cambridge PhD in 1953. He worked in industrial research in the UK (Lever Brothers and Unilever Ltd) and in the USA (Philips Laboratories, Irvington-on-Hudson, NY). He was Assistant Professor of Physical Metallurgy at Harvard University (1954-1959) before moving to the University of Bristol. He became Professor of Physics in 1979. Professor Lang achieved fame for his pioneering studies in X-ray diffraction physics, especially his original technique of X-ray topography, i.e., the 'Lang method' or 'Lang Camera', which displays the internal imperfections in a crystal, such as dislocations, stacking faults, growth-sector boundaries and ferromagnetic domains. The method has been widely used in the non-destructive assessment of crystals for the electronics and diamond industries, among others. Professor Lang studied many types of X-ray diffraction phenomena, including variations from Bragg's law, X-ray moire patterns and other types of fringes. One of his most important discoveries (in collaboration with Professor N. Kato (1923-2002)) was the presence of interference fringes in wedge-shaped perfect crystals, leading to a precise measure of absolute structure amplitude from a unit cell (See the paper, "A study of pendellosung fringes in X-ray diffraction", Acta Cryst. 12, 787 (1959)). Professor Lang is also known for his research using other techniques, such as electron microscopy and cathode-luminescence. In 1964, he was awarded the Charles Vernon Boys Prize of the Institute of Physics and the Physical Society. He was elected a Fellow of the Royal Society in 1975 and was awarded the Royal Society Hughes Medal in 1997. An obituary by Professor M. Moore can be found in the Journal of Applied Crystallography, 41, 825 (2008). The Independent (August 25, 2008) carried an obituary as well.
