lecture2 - 5.61 F all 2007 Lecture #2 page 1 The DEMISE of...

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5.61 Fall 2007 Lecture #2 page 1 The DEMISE of CLASSICAL PHYSICS (a) Discovery of the Electron In 1897 J.J. Thomson discovers the electron and measures ( e m e ) (and inadvertently invents the cathode ray (TV) tube) Faraday (1860’s – 1870’s) had already shown using electrochemistry that amounts of electric current proportional to amounts of some substances could be liberated in an electrolytic cell. The term “electron” was suggested as a natural “unit” of electricity. But Thomson experimentally observes electrons as particles with charge & mass. y = displacement induced by deflector voltage ξ Deflector plates Phosphor Cathode screen Anode Thomson found that results are independent of (1) cathode material (2) residual gas composition “electron” is a distinct particle, present in all materials! Classical mechanics force on electron due to deflector voltage: F y = ξ e (force starts at time t = 0 when electron enters region between plates) dv y dv y = e = m dt ( F = ma ) dt m e Integrating v y = m e e t [Note v y ( t = 0 ) = 0]
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5.61 Fall 2007 Lecture #2 page 2 Integrating again since v y = dy and y t = 0 ) = 0 y =
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This note was uploaded on 04/14/2011 for the course CHEM 2303 taught by Professor Moh during the Spring '11 term at University of Florida.

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lecture2 - 5.61 F all 2007 Lecture #2 page 1 The DEMISE of...

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