GK 2015 Question Bank CD -

Electron : upon it is Based the Whole Science of  Electronics – Joseph John Thomson

Thomson, Sir Joseph John (1856 to 1940) ‘the father of the electron  was  born  in  1856  near Manchester, England.

Scientist Joseph John Thomson was an avid voracious reader, a good student, recipient of John Dalton scholarship — the qualities of a future career of teacher in him; coming events portend signals.

Scientist Joseph John Thomson completed his engineering course at the age of 19, went to Trinity College on a scholarship where he got second rank in Mathematical Tripos, a competitive examination in Cambridge; MPC – Mathematics, Physics and Chemistry, a famous trio of sciences is respected all over, at all times.

Scientist Joseph John Thomson nearly blinded himself in experiments in chemistry.

1. In 1881 he wrote a scientific paper which was a fore­runner of the Einstein Theory.

2. In 1884 Professor of Physics, Trinity College.

3. From 1884 Cavendish Professor 8c Director, Cavendish Research Laboratories for 34 years.

4.Joseph John Thomson married Miss Rose Paget in 1890.

5. Discovered electron in 1895, revolutionalising the atomic structure.

Niels Bohr, in his model of the atom, indicated protons in the nucleus and electrons traveling/orbiting around it.

Electron : it has a rest mass of 9.1 x 10-28 gram which is about 0.0005 i.e. l/2000th of a proton. The electron has a negative charge of electricity. Not all electrons are associated with atoms.

Some occur in a free state in a gas (say, atmosphere) or in vacuum. The electron has an anti-matter counterpart called positron with a positive charge; one annihilates the other on contact.

The velocity of the electron is about 1,60,000 miles per second (the velocity of light 1,86,000 miles per second). How to photograph this electron? Charles T.R. Wilson, the student of Thomson came to his rescue, invented a cloud chamber to photograph atomic particles.

Proton : stable subatomic particle with a positive charge. Its mass is 1.67xl0-27 kg which is 1,836 times the mass of an electron.

In 1920 Ernest Rutherford called hydrogen nucleus as a proton; nitrogen under alpha particle bombardment ejects hydrogen nuclei. Protons are the chief constituents of primary cosmic rays.

Neutron : as the name implies, it has a neutral charge, i.e., zero charge; invented in 1932 by James Chadwick. Its mass is about the same as that of a proton (1840 times that of an electron).

Charged particles can be tackled/controlled by magnets or electric fields, but not neutrons.

6. In 1897 he was crowned “the father of the electron”. In the same year, he declared that cathode rays are units of electric current made up of negatively charged particles of sub-atomic size, viz., electrons. Electronics is the study based on electrons.

7.Scientist Joseph John Thomson was knighted in 1908.

8. Work on isotopes: Isotopes are atoms of the same element which have the same atomic number, same number of protons, but differ in the numbers of neutrons and atomic weight (mass).

Atoms with a net charge are called ions. If a neutral atom loses an electron it becomes a positive ion; if it gains an electron it becomes a negative ion.

Scientist Thomson was a highly gifted teacher. No less than eight of his students distinguished themselves as Nobel Prize winners. His son won Nobel Prize for physics.

But for the discovery of the electron by J.J. Thomson, we would not have been in a position to enjoy TV, electronic video games/camera, to use computer, optoelectronic lasers, electron microscope, to invent industrial robots and such umpteen gadgets.

Scientist Joseph John Thomson was accorded the honor of burial in Westminster Abbey in 1940, a Royal prerogative, on his death at a ripe age of 84.

Scientist Joseph John Thomson left a legacy of textbooks on MPC — mathematics, physics and chemistry, the brilliant trio of basic sciences which makes its students brilliant.