• Tags: davisson-germer, electron-diffraction, verification
• Difficulty: Moderate

Davisson and Germer (1927) verified the de Broglie hypothesis by observing electron diffraction from a nickel crystal surface. They accelerated electrons through 54 V (giving λ = 12.27/√54 = 1.67 Å by de Broglie) and observed a strong diffraction peak at 50° scattering angle. Using Bragg's law (nλ = 2d sinθ, or equivalently nλ = d sinφ for surface diffraction where φ is the scattering angle), the experimental wavelength was 1.65 Å — in excellent agreement with the de Broglie prediction. This experiment conclusively demonstrated the wave nature of electrons and earned a Nobel Prize. G.P. Thomson independently observed electron diffraction through thin metal foils.