American History / The Progressive Era

The Progressive Era

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Autor:  anton  13 December 2010
Tags:  Progressive
Words: 460   |   Pages: 2
Views: 285

Joseph John (JJ) Thomson discovered that atoms are not indivisible; they have a sub-structure that consists of negative particles. JJ and a group of his graduate students designed some tubes containing electrodes inside with the air evacuated from the tubes. They performed some experiments on these tubes where a high voltage electrical current was passed between the two electrodes. Rays proceeded from the Cathode electrode to the Anode electrode.

Thomson further investigated his findings and designed some special tubes that investigated the properties of the Cathode rays to impact against the surface of a Zinc Sulfide coated screen. As the rays got to the surface, there was a spark of light do that the invisible ray’s route could be observed and documented. Then after seeing this, JJ brought an electrical field consisting of a positive plate and a negative plate near the vicinity of the rays. When the electrical current was turned on the ray went toward the positive plate and away from the negative plate. This experiment proved that the rays had a negative charge.

In 1904 JJ Thomson suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces. His attempt to estimate the number of electrons in an atom from measurements of the scattering of light, X, beta, and gamma rays led to the research his student Ernest Rutherford continued. Thomson ‘s last important experimental project focused on determining the nature of positively charged particles. Here his techniques led to the development of the mass spectroscope, an instrument perfect by his assistant, Francis Aston, who received a Nobel Prize for it in 1922.

Growing up, Thomson’s father had wanted him to become an engineer, but it required apprenticeship, which cost to much for the family to pay for. Instead Thomson attended Owens College, Manchester, which had a good science program and faculty. He then was recommended to Trinity College, Cambridge, where he became a mathematical physicist. In 1884 he was named to the Cavendish Professorship of Experimental Physics at Cambridge, although he really didn’t do much experimental work. He was said to be clumsy with his hands, but he had a great capacity for learning. He was also very good at designing an apparatus and diagnosing its problems. These type of skills are valuable not only in science but in other fields of work as well. He became a great teacher, who could command the entire attention of a class and he encouraged his students. Of all the physics associated with determining the structure of the atom, Thomson remained the most closely aligned to the chemical community.


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