Discovered by : J. J. Thomson
Discovered in year : 1897
Electron is an elementary particle with negative charge It is the lightest particle having a non-zero rest mass. It belongs to the lepton class of particles and, together with its antiparticle, the positron, and its associated neutrino and antineutrino, constitutes a subfamily of the leptons. The Discovery of Electron was made in 1897 by J. J. Thomson, who showed that cathode rays are composed of electrons and who measured the ratio of charge to mass for the electron. Joesph John Thomson (1856-1940) was the son of a Manchester bookseller. He entered college at fourteen and at twenty-eight was elected a fellow of the Royal Society and appointed to the Chair of Physics at the Cavendish Laboratory.
His great discovery occurred in 1897 during the course of his investigations of cathode rays. Thomson provided convincing evidence that the rays consisted of charged particles; he measured the ratio of charge to mass and was able to estimate that the mass was equal to about 1/1800 of the mass of a hydrogen atom. His discovery of the electron won the Nobel Prize in 1906 and he was knighted two years later. The name electron was first used for a unit of negative electricity by the English physicist G. J. Stoney in the late 19th cent.
Development in the Discovery of Electron
In 1909, R. A. Millikan measured the charge of the electron. Combining these two results gives the mass of the electron (about 1/1,840 of the mass of the proton). Ernest Rutherford, in 1903, showed that beta rays are high-energy electrons. In 1927, Davisson and Germer, working with high-speed electron beams, discovered that electrons sometimes exhibit the wave property of diffraction. This confirmed L. V. de Broglie's hypothesis that electrons, which had previously been thought of as particles, also possess certain wave properties . The wavelike properties of electrons are utilized in the electron microscope and other devices.
Role of Electron in the Improvement Of Human Life
- The discovery of the wave like character of the electron helped in the making of the modern electron microscope
- Electron beams are used in welding and lithography. Electron beam processing is used to irradiate materials in order to change their material properties or sterilize medical and food products
- Electron beams are used in Radiation Therapy. These beams are generated by linear accelerators for treatment of superficial tumors. Because an electron beam only penetrates to a limited depth before being absorbed, it is useful for treating skin lesions such as basal cell carcinomas.
- Polarized electron beams are useful for various experiments.
- Electrons are at the heart of cathode ray tubes, which are used extensively as display devices in laboratory instruments, computer monitors and television sets.
