Walter Kaufmann (5.07.1871-1.01.1947) was a German physicist. He was born in Elberfeld. He graduated from the University of Munich (1894). In 1896-98 he worked at the Institute of Physics in Berlin, in 1899-1902 at Göttingen, and in 1903-07 at the University of Bonn. In 1908 —35 he was professor and director of the Institute of Physics of the University of Königsberg.
His research was in the field of mechanics, aerodynamics, hydromechanics and atomic physics. He studied the deflection of the particles of cathode rays in a magnetic field (1896 — 98) and of the beta rays of radium in electric and magnetic fields (1899—1902), and determined the ratio of charge to mass for them. He was the first to prove experimentally (1902) that the mass of the electron depends on its velocity.