The Franck-Hertz Experiment* In , James Franck and Gustav Hertz performed an experiment which demonstrated the existence of excited states in mercury atoms, helping to confirm the quantum theory which predicted that electrons occupied only discrete, quantized energy states. In , by James Franck and Gustav Ludwig Hertz. One year after Bohr's theory of quantized energy states. Nobel Prize in “for their discovery of the. Thus the Franck-Hertz experiment combines the physics of collision with the 2 Theory. Franck-Hertz tube. Figure 1: Franck-Hertz tube.


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Only the direction of franck hertz experiment theory is changed. Inelastic collisions - The electron excites the gas atom and loses energy. Due to the discrete energy levels, this can only happen for a precise value of energy.

This is called the excitation energy and corresponds to the difference in energy between the atomic ground state lowest possible energy and a franck hertz experiment theory energy level. A - No current is observed.

The accelerating voltage isn't strong enough to overcome the stopping voltage.

The Franck-Hertz Experiment: A Demonstration of Quantum Theory

Hence, no electrons reach the anode and no current is produced. B - The current rises to a 1st maximum. The accelerating voltage becomes sufficient to give the electrons enough energy to franck hertz experiment theory the stopping voltage but not enough to excite the gas atoms.

As the acceleration voltage increases the electrons have more kinetic energy. C - The current is at the 1st maximum.

Franck-Hertz experiment

The accelerating voltage is now sufficient to give electrons enough energy to excite the gas atoms. Inelastic collisions can begin.


After an inelastic collision, the electron may not have enough energy to overcome the stopping potential so the current will start to drop. D - The current drops from the 1st maximum. Fortunately, other scientists quickly realized how this experiment did confirm Bohr's hypothesis that atoms make only certain transitions between discrete energy states.

So, the idea is that when an electron runs into a mercury atom, there are two outcomes. That leaves the electron with very little kinetic energy. Let's look at what happens inside their apparatus. Harmonic Motion and Waves Virtual Lab Harmonic Motion and Wave lab is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound all mechanical franck hertz experiment theory in gases, liquids, and franck hertz experiment theory.

The study of this lab revolves around the generation, propagation and reception of mechanical waves and franck hertz experiment theory. Modern Physics Virtual Lab Modern physics refers to the post-Newtonian conception of physics developed in the first half of the 's.

These concepts embody the study of tiny subatomic particles or lightening fast speeds. This behavior is typical of true vacuum tubes that don't contain mercury vapor; larger voltages lead to larger " space-charge limited current ".

Franck–Hertz experiment - Wikipedia

The current then increases steadily franck hertz experiment theory again as the voltage is increased further, until 9. While it isn't evident in the original measurements of the figure, this series of dips in current at approximately 4.

They franck hertz experiment theory using a quantum relationship between the energy of excitation and the corresponding wavelength of light, which they broadly attributed to Johannes Stark and to Arnold Sommerfeld ; it predicts that 4.

The figure is based on the original spectra franck hertz experiment theory by Franck and Hertz in The fact that the Franck—Hertz tube emitted just the single wavelength, corresponding nearly exactly to the voltage period they had measured, was very important. Electrons traveling slowly change direction after elastic collisions, but do not change their speed.