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Today in History: Franck-Hertz experiment proves quantum mechanics theory

4/24/2026

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Story summary

On April 24, 1914, James Franck and Gustav Hertz presented the Franck–Hertz experiment to the German Physical Society. This groundbreaking experiment demonstrated the quantum nature of atoms by showing that electrons lose specific amounts of kinetic energy when colliding with mercury atoms, marking a significant advancement in the understanding of quantum mechanics.

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Story summary

On April 24, 1914, James Franck and Gustav Hertz presented the Franck–Hertz experiment to the German Physical Society. This groundbreaking experiment demonstrated the quantum nature of atoms by showing that electrons lose specific amounts of kinetic energy when colliding with mercury atoms, marking a significant advancement in the understanding of quantum mechanics.