Carl D Anderson (1905-1991) discovered the positron by accident in 1932. He was photographing the tracks of cosmic rays in a cloud chamber to find the energy spectrum of secondary electrons produced by the rays. A lead plate, to slow or stop the rays divided the chamber, and a magnetic field applied to deflect the particles in different directions according to their mass. Many positive particles were observed which were too light and produced too little ionisation to be protons. Anderson concluded that they were positive electrons, or positrons.

Picture Reference: 10296273
Subject: SCIENCE & TECHNOLOGY > Atomic & Nuclear Physics > Particle Imaging, Cloud Chamber
Inventory No.: 1937-0231
Credit: Science Museum

Keywords: 1930s, 1900s, 20th Century, Anderson, Anderson, Carl, Atom, Atom Tracks, Carl, Chamber, Cloud, Cloudy, Environmental, Environmental Science, Imaging, Meteorology, Natural World, Particle, Particle Imaging, Cloud Chambe, Positron, Track, Transportation, Transport, United States, United States Of America, Weather Condition

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