Frank Hertz Experiment

We are offering Franck-Hertz Experiment useful in Physics and Material Science Lab. This experiment verifies that:

• It is possible to excite atoms by low energy electron bombardment.
• The energy transferred from electrons to the atoms always had discrete values.
• The values so obtained for the energy levels were in agreement with spectroscopic results.

Thus the existence of atomic energy levels put forward by Bohr can be proved directly. It is a very important experiment and can be performed in any college or University level laboratory.
The Experiment is consists of the following:

• Argon filled tetrode
• Filament Power Supply: 3.6-3.4V continuously variable
• Power Supply for VG1K: 1.3-5V continuously variable
• Power Supply for VG2A: 1.3 - 12V continuously variable
• Power Supply for VG2K: 0 - 95V continuously variable
• Saw tooth waveform for CRO display  Scanning Voltage : 0-80V               Scanning Frequency : 115±20 Hz
• Multirange Digital Ammeter               Display : 3½   digit, LED
  Range : 10-7, 10-8 & 10-9 A

The instrument can, not only lead to a plot of the amplitude spectrum curve by means of point by point measurement, but also directly display the amplitude spectrum curve on the oscilloscope screen. This instrument can thus be used as a classroom experiment as well as for demonstration to a group of students.

Analysis of data:

Data obtained for the excitation potential point by point are shown in Fig. 3. The readings are taken for 1V changes on grid 2 (VG2K). A significant decrease in electron (collector) current is noticed every time the potential on grid 2 is increased by approximately 12V, thereby indicating that energy is transferred from the beam in (bundles) "quanta" of 12eV only. Indeed, a prominent line in the spectrum of argon exists at 1048Å corresponding to eV=11.83.