Second, two years later In 1949, analysing plates exposed at the Sphinx Observatory on the Jungfraujoch in Switzerland, first precise observations of the positive K-meson and its ‘strange’ decays were made by Rosemary Brown (now Rosemary Fowler), a research student in Cecil Powell 's group at Bristol. Then known as the ‘Tau meson’ in the Tau-theta puzzle, precise measurement of these K-meson decay modes led to the introduction of the quantum concept of Strangeness and to the discovery of Parity violation in the weak interaction. Rosemary Brown called the striking four-track emulsion image, of one 'Tau' decaying to three charged pions, her "K track", thus effectively naming the newly discovered ‘strange’ K-meson. Cecil Powell was awarded the 1950 Nobel Prize in Physics "for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method".