When Thomson passed electricity through matter inside a glass container, he observed luminescence on the glass (evacuated of air). He visualizes negatively charged electron.
The cathode ray tube studies of J.J. Thomson demonstrated that all atoms contain minute, electron-like subatomic particles that are negatively charged. Thomson proposed the plum pudding model of the atom, which had positively charged "soup" and negatively charged electrons within.
In 1897, Thomson carried out a superior vacuum version of Hertz's test. In a tube's end, he directed the cathode rays between two parallel metal plates, where they were seen luminescence on the glass. The rays went downward when the top metal plate was negative and upward when the top plate was positive.
The deflection followed a linear relationship with the potential difference between the plates. It was evident that cathode rays were negatively charged particles because of the magnetic and electric deflections that were seen. Thomson's finding proved that electricity is a particle substance. He referred to his particles as electrons as a result.
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