|
Towards the end of the 19th
century Joseph J.Thomson (1856-1940) was studying
electric discharges at the well-known Cavendish
laboratory in Cambridge, England. Several people had
been studying the intriguing effects in electric
discharge tubes before him. Spectacular glows could
be observed when a high voltage was applied in a gas
volume at low pressure. It was known that the
discharge and the glow in the gas were due to
something coming from the cathode, the negative pole
of the applied high voltage. Thomson made a series of
experiments to study the properties of the rays
coming from the cathode. He observed that the cathode
rays were deflected by both electric and magnetic
fields - they were obviously electrically charged. By
carefully measuring how the cathode rays were
deflected by electric and magnetic fields, Thomson
was able to determine the ratio between the electric
charge (e) and the mass (m) of the rays. Thomson's
result was
e/m = 1.8 10-11
coulombs/kg.
The particle that J.J.Thomson
discovered in 1897, the electron, is a constituent of
all the matter we are surrounded by. All atoms are
made of a nucleus and electrons. He received the
Nobel Prize in 1906 for the discovery of the
electron, the first elementary particle.
|
The Nobel
Prize in Physics 1906 - Sir Joseph John Thomson
»
