Before revision: 65–66 Discovery of the electron In 1897, J. J. Thomson discovered that cathode rays are not a form of light but made of negatively-charged particles because they can be deflected by electric and magnetic fields.
After revision: 65–66 Discovery of the electron In 1897, J. J. Thomson discovered that cathode rays are not a form of light but made of negatively charged particles because they can be deflected by electric and magnetic fields.