Wave-particle duality is the concept in quantum physics that particles like electrons exhibit both wave-like and particle-like behavior. This duality was dramatically demonstrated in electron diffraction experiments.
In these experiments, a beam of electrons is directed at a thin crystal or a double-slit barrier. Instead of behaving like tiny solid particles and forming a sharp impact pattern, the electrons create an interference pattern—a hallmark of waves. This pattern closely resembles the kind seen when light or water waves pass through slits and interfere with each other.
This unexpected result proved that electrons—traditionally considered particles—also act like waves, with a wavelength described by the de Broglie hypothesis. The wave nature of electrons is now fundamental to technologies like electron microscopes, which rely on electron waves for high-resolution imaging.
Electron diffraction thus confirmed that matter is not strictly particle-like or wave-like but can behave as both, depending on how it’s observed—a cornerstone of quantum mechanics.