Franck-Hertz experiment, Setup and findings
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The Franck Hertz experiment was first studied in 1914 by James Franck and Gustav Hertz and presented to the German Physical Society. It was the first electrical measurement to show the quantum nature of atoms. The Franck Hertz experiment consisted of a vacuum tube designed to study the energetic electrons that flew through a thin vapour of mercury atoms. It was discovered that only a specific amount of an atom’s kinetic energy would lose as the electrons collide with the mercury atom.
Franck Hertz Experiment
Aim:
To demonstrate the concept of quantisation of the energy levels according to the Bohr’s model of an atom.
Materials Required:
Following are the list of materials required for this experiment:
Oven
A control unit for power supply
A DC amplifier
Mercury filled Franck-Hertz tube
Neon filled Franck-Hertz tube
Theory:
The original experiment used a heated vacuum tube of temperature 115 °C with a drop of mercury of vapour pressure 100 Pa. Three electrodes, an electron-emitting hot cathode, a metal mesh grid, and an anode are attached to the tube. To draw the emitted electrons, the grid’s voltage is made positive with respect to the cathode. The electric current measured in the experiment results from the movement of electrons from the grid to the anode. The electric potential at the anode is slightly more negative than the grid so the electrons have the kinetic energy the same as in the grid. The Franck Hertz experiment was explained in terms of elastic and inelastic collisions between the electrons and the mercury atoms.
The graphs show the dependence of the electric current flowing out of the anode and the electric potential between the grid and the cathode. Following are the observations from the graph:
With the steady increase in the potential difference, the current increases steadily through the tube.
The current drops almost to zero at 4.9 volts.
Again there is an increase in the current as voltage increases to 9.8 volts.
Again a similar drop is observed at 9.8 volts.
Energy absorption from electron collisions in the case of neon gas is seen.. When the accelerated electrons excite the electrons in neon to upper states, they de-excite in such a way as to produce a visible glow in the gas region in which the excitation is taking place. There are about ten peak electrons levels in the range of 18.3 to 19.5 eV. They de-excite by dropping to lower states at 16.57 and 16.79 eV. This energy difference gives the light in the visible range.
Who first conducted the Franck Hertz experiment?
In 1914, James Franck and Gustav Hertz performed the Franck Hertz experiment.
Which experiment explained elastic and inelastic collisions between the electrons and the mercury atoms?
Franck Hertz experiment.
Franck Hertz experiment supports which model of atom?
This experiment supports the Bohr model of atoms.
Under which condition bodies undergo inelastic collision?
When the two bodies whose kinetic energies are not conserved due to internal friction undergo inelastic collision.
My left ear loved this video!
Sorry for the mono sound..can't change now 😅
Really EXCELLENT presentation. it would be great to see an equivalent presentation for the Stern-Gerlach experiment.
Thank you for your kind comment. Great suggestion! Surely
❤
Very good presentation. Easy to understand
Lovely explanation and video, thank you!
Glad you found it helpful!
Extreme amazing and easy to learn. Thanks physics partner
Wow such a nice presentation....i like this method very much 🙂 thank you ❤️
Thank you very much for appreciation
Sir, is the 4.9V at the peak or the trough … because it seems you said trough but the scale on the x axis demonstrates that the peak is when the accelerating voltage is 4.9V … thanks in advance for answering
If the graph indicates that the peak occurs at 4.9V, then it is indeed correct to say that this voltage is associated with the peak of the current, not the trough.
Awesome thanks sir 🎉
Thank you
Awesome
Not describe the band concept
The band concept in relation to the Franck-Hertz experiment refers to the observation of distinct energy bands in the experiment's results. When energetic electrons pass through a thin vapor of mercury atoms in the Franck-Hertz tube, they undergo elastic and inelastic collisions with the mercury atoms. According to the model for these collisions, there should be narrow bands of energy where the electrons experience inelastic collisions and lose a specific amount of kinetic energy .
These energy bands correspond to the quantized energy levels of the mercury atoms. The experiment demonstrated that electrons can only lose or gain energy in discrete amounts, supporting the concept of energy quantization in atoms. The observation of these energy bands provided evidence for the quantum nature of atoms and confirmed the predictions of the Bohr model of the atom .
In summary, the band concept in the Franck-Hertz experiment refers to the observation of distinct energy bands that correspond to the quantized energy levels of the mercury atoms, demonstrating the quantization of energy in atoms and supporting the quantum theory
Seems as if you're reading
Thank you
Ye
It's mono... Jesus Christ.
Elaborate please
@@physicspartner I hear mono sound when you're talking. Intro is in stereo (how it should be).