Franck-Hertz Experiment

Electrons crossing mercury vapor lose energy only in 4.9-volt steps, proving atomic energy levels are real.

Core Principles & Analysis

• Franck and Hertz measured current dips every 4.9 volts as electrons excited mercury atoms.
• It was the first direct electrical evidence for the quantized energy levels of Bohr’s 1913 atomic model.
• The pair received the 1925 Nobel Prize in Physics for the discovery.

Specifications & Metrics

• YEAR: 1914