How did the Franck-Hertz experiment support quantum theory?
The core of the Franck-Hertz experiment lies in its observation of specific energy transfer. Let us first observe what nature tells us. When electrons, accelerated to precise voltages, collided with mercury atoms, they could only excite the atoms if their energy precisely matched the difference between two allowed energy states of the atom. If the electron's energy was not exactly right, it would simply bounce off without transferring energy in a way that caused excitation. The evidence suggests this showed that atoms possess discrete, quantized energy levels, meaning they cannot exist with arbitrary amounts of energy. This directly validated Bohr's model and the broader quantum mechanical framework.
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