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Technical data

Franck-Hertz experiment with a Ne-Tube

Article no: P2510315

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Principle

Electrons are accelerated through a gas of neon atoms. As the electrons collide with the neon atoms, they transfer energy. However, energy transfer only occurs when the electrons have enough energy to excite the neon atoms to a higher energy state. This results in a drop in the current, which is detected as peaks on a voltage-current graph. The neon atoms then emit light as they return to their ground state, producing visible spectral lines. The excitation energy of neon is determined from the distance between the equidistant minima of the electron current in a variable opposing electric field. This experiment provides direct evidence of quantized atomic energy levels.

Benefits

Fascinating Nobel Prize experiment (Franck-Hertz 1925)
Suitable for demonstration and lab courses as well
Compact neon tube in sturdy casing - ready to use due to short heat-up time
Control unit compatible to Ne and Hg tube
Easy-to-use software for control, data acquisition and evaluation

Tasks

To record the counter current strength I in a Franck-Hertz tube as a function of the anode voltage U.
To determine the excitation energy E from the positions of the current strength minima or maxima by difference formation.

Learning objectives

Energy quantum
Quantum leap
Electron collision
Excitation energy