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How did the Davisson-Germer experiment demonstrate electron diffraction?

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A horizontal gradient bar displays the visible light spectrum from violet to red, labeled with corresponding frequency in terahertz, wavelength in nanometers, and photon energy in electron volts. — light When white light is spread apart by a prism or a diffraction grating, the colours of the visible spectrum appear. The colours vary according to their wavelengths. Violet has the highest frequencies and shortest wavelengths, and red has the lowest frequencies and the longest wavelengths.

The Davisson-Germer experiment did not demonstrate electron diffraction by treating electrons as light; rather, it provided experimental evidence that electrons—previously considered only as particles—exhibit wavelike properties, similar to how light displays both wave and particle characteristics.123

In 1927, Clinton Davisson and Lester Germer confirmed the hypothesis proposed by Louis de Broglie that matter possesses a wavelength inversely proportional to its momentum ( $λ = h / p$ ). By directing a beam of monoenergetic electrons at a nickel crystal, they observed that the electrons reflected off the crystal faces in specific diffraction patterns.431

These patterns were analogous to those produced by X-rays and other electromagnetic waves, demonstrating that the electrons underwent interference due to their wavelike nature. This discovery was a foundational moment for quantum mechanics, verifying the principle of wave-particle duality for subatomic particles.142