Scattering experiments in Manchester
Geiger studied physics in Erlangen and Munich before becoming Ernest Rutherford’s assistant in Manchester. In 1909 he and the undergraduate Ernest Marsden investigated alpha-particle scattering by thin metal foils. A small fraction of particles underwent large deflections, an observation that informed Rutherford’s later nuclear model of the atom.
A laboratory for radioactivity
In 1912 Geiger joined the Physikalisch-Technische Reichsanstalt and helped establish its radioactivity laboratory, leading the group from the following year. Its work included radioactive sources for medical use. He later held university posts in Kiel, Tübingen and Berlin.
References: [1]
Radiation-counting tubes
Geiger’s gas-filled counters used amplification by ionisation to register very small radiation events. With Müller he developed this approach into the Geiger–Müller tube in 1928. Radiation detection became a second major strand of his work alongside the earlier scattering experiments.
References: [1]