🔬 Davisson–Germer — a sharp electron-scattering peak appears at 54 V
Fire a beam of electrons, accelerated through a voltage V, at a nickel crystal and swing a detector around it. The scattered intensity shows a sharp maximum at φ ≈ 50° when V ≈ 54 V — a diffraction peak. It matches the de Broglie wavelength λ = h/√(2meV): electrons behave as waves.
An electron gun accelerates electrons through a voltage V and fires the beam at a nickel crystal.
λ = h/√(2meeV) = 1.227/√V nm · nickel spacing d ≈ 0.215 nm
de Broglie λ = — nm · scattered intensity I = — % (peaks at 54 V, φ = 50°)