Explain Davisson and Germer experiment to verify the wave nature of electrons

Early atomic models could explain only the particle nature of electrons, but not their wave-like properties. In 1927, C.J. Davisson and L.H. Germer provided experimental evidence of the wave nature of electrons through their famous electron diffraction experiment.

Experimental Setup

1. An electron gun with a tungsten filament coated with barium oxide was heated using a low-voltage power supply.
2. The gun emitted electrons, which were accelerated by a high-voltage source through a potential difference.
3. The accelerated electrons passed through a cylinder with fine holes, forming a collimated electron beam.
4. This beam was directed onto the surface of a nickel crystal, causing the electrons to scatter in different directions.
5. A movable electron detector, connected to a sensitive galvanometer, measured the intensity of scattered electrons at different angles on a circular scale.

Key Observations

• Changing the scattering angle caused variations in the intensity (I) of the scattered electrons.
• By varying the accelerating voltage from 44 V to 68 V, different diffraction patterns were obtained.
• A sharp intensity peak was observed at an accelerating voltage of 54 V and a specific scattering angle.
• This peak was caused by the constructive interference of electrons diffracted by regularly spaced atoms in the nickel crystal.
• From this diffraction pattern, the wavelength of the electrons was calculated as 0.165 nm, matching de Broglie’s prediction.

Conclusion

• The Davisson–Germer experiment confirmed that electrons exhibit wave-like behavior in addition to their particle nature.
• The diffraction patterns clearly demonstrated the wave–particle duality of matter, supporting de Broglie’s hypothesis.

The Davisson–Germer experiment is central to understanding electron diffraction and the dual nature of matter. While the theory involves equations and applications that may seem complex, mastering the fundamentals makes it easier. Students are encouraged to use reliable textbooks and reference materials for clear explanations rather than relying solely on shortcuts.