The particle-wave duality of matter is one of the fundamental principles of quantum mechanics, which describes the behavior of particles at the atomic and subatomic levels. It suggests that particles, such as electrons, photons, and even larger entities like atoms and molecules, can exhibit both particle-like and wave-like properties, depending on how they are observed or measured.
The wave-like behavior of matter was first proposed by Louis de Broglie in 1924, who suggested that if light, which was known to exhibit wave-like properties, could also behave as particles (photons), then particles of matter should also exhibit wave-like properties. De Broglie's hypothesis was experimentally confirmed by the famous electron diffraction experiments conducted by Clinton Davisson and Lester Germer in 1927, which showed that electrons can behave like waves when passing through a crystal lattice.
The explanation of particle-wave duality lies in the mathematical formalism of quantum mechanics, specifically the wave-particle nature of the wave function. In quantum mechanics, particles are described by wave functions that evolve over time according to the Schrödinger equation. The wave function contains information about the probability distribution of the particle's position and other observable properties.
When a particle is observed or measured, its wave function "collapses" into a particular state, corresponding to a specific measurement outcome. This collapse is often described as the particle "manifesting" as a localized entity, behaving like a particle with a definite position and other properties.
However, between measurements, the particle's wave function evolves according to the laws of quantum mechanics, and it can exhibit wave-like behavior, including interference and diffraction patterns. These wave-like properties are particularly evident when dealing with systems of particles, such as electrons passing through a double-slit experiment or interacting with a crystal lattice.
It's important to note that the wave-particle duality is a fundamental property of quantum mechanics and is not easily explained or visualized in terms of classical intuition. Quantum mechanics provides a mathematical framework that accurately describes the behavior of particles at the microscopic level, but it often challenges our classical intuitions about the nature of reality.