Wave-particle duality

The observation that Elementary particles and light exhibit properties of both Waves and particles depending on how they are measured or observed. This central paradox of Quantum mechanics reveals that nature does not fit neatly into classical categories—an Electron or Photon is neither purely a localized particle nor a spreading wave, but something stranger that behaves like either when interrogated by experiment.

The puzzle emerged in the early 20th century as physicists studied light and matter. Newton's corpuscular theory of light clashed with evidence of Interference and Diffraction patterns. Later, observations of the Photoelectric effect suggested light came in discrete packets. Electrons similarly defied categorization: they produced interference fringes in the double-slit experiment yet arrived as distinct impacts on detectors.

This ambiguity is not mere ignorance—it reflects something fundamental. The Measurement Problem (quantum mechanics) suggests the act of observation itself collapses a system's potential states into one outcome. An unmeasured electron exists in a Superposition of possibilities described by a wave function; measure its position and the wave "collapses" into a particle.

Wave-particle duality is formalized through Mathematical models like the Schrödinger equation and concepts such as De Broglie wavelength. It underscores that reality at quantum scales operates by rules alien to everyday Intuition.

Related

Quantum mechanics, Photon, Electron, Double-slit experiment, Superposition