Post on 06-Jul-2015
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JJ THOMSON EXPERIMENT (1897)
CATHODE RAY TUBE
EXPERIMENT 1
CATHODE RAY TUBE
Source ofElectricalPotential
Metal Plate
Gas-filledglass tube Metal plate
Stream of negativeparticles (electrons)
A Cathode Ray Tube
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 58
Thomson’s Experiment
Anode +- cathode
Thomson’s Experiment
- cathode anode +
Thomson’s Experiment
• Passing an electric current makes a beam appear to move from the negative to the positive end.
- +
Thomson’s Experiment
• Passing an electric current makes a beam appear to move from the negative to the positive end.
- +
INFERENCE????
•A stream of particles could be seen to flow from cathode to anode.
Experiment 2
INFERENCE?• THE CAUSE OF THE GLOW IS THE INVISIBLE RAYS EMITTED FROM THE NEGATIVE METAL PLATE OF THE DISCHARGE TUBE.
EXPERIMENT 3
ON APPLICATION OF ELECTRICAL FIELD
Thompson’s Experiment
•By adding an electric field
Thompson’s Experiment
• By adding an electric field
Thompson’s Experiment
•By adding an electric field he found the moving particles were negative
INFERENCE
•THE GLOW IS PRODUCED BY NEGATIVELY CHARGED PARTICLES.
EXPERIMENT 4
CHANGED CONDITIONSBUT
SAME RESULT OBTAINED
INFERENCE?
•THERE ARE NEGATIVELY CHARGED PARTICLES IN ALL SUBSTANCES.
THUS, ELECTRONWAS DISCOVERED
JJ THOMSON MODEL OF ATOM-PLUM PUDDING MODEL
THANKYOU