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United Scientific Supplies Franck-Hertz Apparatus II

The Franck-Hertz experiment yields basic evidence for the existence of quantum states.

Supplier:  United Scientific Supplies FHA002

Catalog No. S43701

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  • The Franck-Hertz Apparatus II is an improved model of the well-known Franck-Hertz Apparatus (FHA001), featuring stable, updated electronics and robust digital readouts for voltage and current.
  • New fully shielded coax cables reduce electrical noise.
  • The Franck-Hertz Experiment yields basic evidence for the existence of quantum states.
  • Inside a vacuum tube filled with a trace of Ar gas, a beam of electrons is generated and accelerated towards a counter electrode.
  • A voltage barrier ahead of the counter electrode only allows electrons with a certain minimum energy to get through and make a detectable current.
  • As the accelerating energy is increased, changes in the current are observed.
  • On the way to the counter electrode, electrons collide with Ar atoms.
  • As the electron energy rises, it gives one quantum of energy to the Ar for ionization.
  • Now the electron can’t pass the voltage barrier and the current drops.
  • Valleys in the current curve are evidence of the donations of a quantum of energy.
  • Ar-filled Franck-Hertz tube achieves 5-7 current maxima.
  • Anode current range 0.1 nA—1 μA.
  • Automatic scan to oscilloscope or chart recorder, or manual scan.
  • Adjustable, stabilized filament, grid, and anode voltages.
  • 3-1/2 digit voltage and current readouts.
  • Requires user-supplied dual-channel oscilloscope for automatic scan.


12 to 15
Franck-Hertz Apparatus II
Advanced Physics
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