IN-DEPTH LOOK 5.2 - Electricity and Magnetism 147 IN-DEPTH...

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Electricity and Magnetism 147 IN-DEPTH LOOK 5.2: THE DISCOVERY OF THE ELECTRON How was the electron discovered? In the 1850s through the 1890s, several German and British physicists were studying a peculiar phenomenon—a glowing gas in a glass tube containing a low-pressure atmosphere. A glass tube, with two metal wires inserted through the walls, was partially evacuated of air. When the two wires were hooked to opposite sides of a battery , as illustrated in Figure 5.4 , a glow was observed in the low- pressure air between the wires. This was the precursor of the modern-day F uorescent light bulb, but at that time, scientists did not know what caused the glow. They suspected that some kind of “rays” were emitted by the cathode, and they called these cathode rays. They did not know what the rays consisted of. In 1897, J. J. Thomson, a physics professor at Cambridge University in England, con- structed a different design of tube, illustrated in Figure 5.5 . He reasoned that if the cath-
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This note was uploaded on 09/29/2011 for the course PHYS 222 taught by Professor Wade during the Spring '09 term at Edmonds Community College.

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