The wave-particle duality of light and matter is a fundamental concept in quantum physics that describes the dual nature of particles, such as electrons, photons, and other quantum entities. It is indeed puzzling and counterintuitive that particles can exhibit both wave-like and particle-like behavior.
In quantum field theory (QFT), which is the framework for describing quantum interactions, particles are treated as excitations of underlying fields. These fields pervade all of space and interact with one another according to certain rules. The behavior of these fields and their excitations can be described by wave-like equations, such as the Schrödinger equation or the wave equation of quantum field theory.
The wave-like properties of particles in QFT are a consequence of the probabilistic nature of quantum mechanics. When particles are not being measured or observed, they exist in a superposition of states, represented by a wavefunction. This wavefunction encodes the probability distribution for various outcomes of measurements.
However, when a measurement is performed, the wavefunction "collapses" into a specific state, and the particle behaves as a localized entity with well-defined properties, such as position or momentum. This collapse is known as wavefunction collapse or measurement collapse.
The wave-particle duality arises because particles can exhibit interference and diffraction patterns, similar to waves, under certain experimental conditions. This behavior is observed in experiments like the double-slit experiment, where particles can produce an interference pattern, even though they are detected as discrete particles at individual locations.
The exact interpretation of wave-particle duality and the collapse of the wavefunction is still a subject of philosophical and interpretational debate in quantum mechanics. Various interpretations, such as the Copenhagen interpretation or the Many-Worlds interpretation, provide different perspectives on the underlying nature of quantum phenomena.
In summary, the wave-particle duality of light and matter arises from the probabilistic nature of quantum mechanics and the mathematical framework of quantum field theory. Particles in QFT exhibit wave-like properties due to the behavior of underlying fields, and their wave-like behavior can be observed under certain experimental conditions, while they can also manifest as localized particles during measurements.