Joseph John Thompson was born in Manchester on December the 18th 1856, and attended Owens College Manchester before winning a scholarship to study mathematics at Trinity College Cambridge. In JJ Thompson was appointed a fellow of Trinity College, and then Cavendish professor of experimental physics in 1884. JJ Thompson went on to win the Nobel Prize for Physics in 1906 for his work on the electron and the conduction of electricity by gases. JJ Thompson was also awarded a knighthood in 1908. JJ Thompson died on August the 30th 1940
JJ Thompsons discovery of the electron was the first sub atomic particle to be discovered, and led him to formulate the first modern model of the atom, the plum pudding model. This however was later superseded by one of his pupils, Rutherford, improved model.
JJ Thompson discovered the electron through his work on cathode rays, he then went on to find the charge/mass ratio of the electron.
The Cavendish Laboratory
JJ Thompson discovered the electron by experiments that showed cathode rays had momentum. For an object to have momentum it must have a mass, so the cathode ‘rays’ must actually be a stream of particles, electrons.
JJ Thompson also found the charge/mass ratio using cathode rays. He did this by deflecting the cathode rays with magnetic and electric fields, and measuring the deflection. This allowed him to find the charge/mass ratio because the degree to which the particles are deflected is related to the particles momentum, and charge. The value he arrived at for this ratio was 1.76x108 C/g
The Cathode ray setup JJ Thompson used:
