Anonymous asked in Science & MathematicsPhysics · 1 decade ago

Franck - Hertz experiment?

When are the photons likely to be emitted in the Franck-Hertz experiment?

1 Answer

  • Anonymous
    1 decade ago
    Favorite Answer

    The Franck-Hertz experiment is an experiment in which energy levels of gas atoms are demonstrated by sending electrons with known kinetic energies through the gas until they are absorbed.

    The idea is that when the electrons have an amount of kinetic energy that can be absorbed by the gas atoms, much fewer of them will pass through than when they have an amount of energy that the gas atoms CANNOT absorb.

    But, when the gas atoms absorb kinetic energy from electrons, they very quickly release this energy in the form of photons. So, you should expect photons to be emitted when the electrons have at least as much energy as the first absorption wavelength of the gas atoms.

    The original Franck-Hertz experiment was done with mercury vapor, which begins absorbing kinetic energy and emitting photons when the electrons have about 4.9eV, which occurs when a potential of 4.9 volts is applied to the chamber.

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