franckhertz - Note-A-Rific: Franck-Hertz Experiment...

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Note-A-Rific: Franck-Hertz Experiment Franck-Hertz Experiment In 1914 James Franck and Gustav Hertz set up an apparatus to try to work out some of the mysteries that still surrounded the model of the atom that Bohr had proposed. They set up the following apparatus… ( detailed diagram on page 839 in the text) 1. Electrons are emitted from the cathode . 2. A voltage that can be adjusted to increase the positive charge on the screen accelerates them, giving them kinetic energy. 3. Most of the electrons easily pass through the screen and hit the anode … so the ammeter shows a current flowing. 4. As the voltage is increased the current increases. Note: since we are accelerating electrons throughout this section, if a voltage is used to accelerate them they will gain energy that can be easily stated in electron volts (eV). Example : An electron accelerated by 5.2V will have 5.2eV of kinetic energy.
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Here’s the interesting part… fill up the tube with mercury vapour. They used mercury because they could easily put liquid mercury into the tube and let it evaporate into a gas once the tube was sealed. Now there’s something for the electrons to bump into. We would expect that not as many electrons will make it to the anode, so the current might drop off a bit. The data
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This note was uploaded on 02/29/2012 for the course PHYS 227 taught by Professor Rabe during the Fall '08 term at Rutgers.

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franckhertz - Note-A-Rific: Franck-Hertz Experiment...

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