The wave-particle duality is a fundamental concept in quantum mechanics, but it is important to note that it does not mean that light (or any other quantum entity) exists simultaneously as a wave and a particle in the classical sense. Rather, it suggests that the behavior of quantum entities can exhibit characteristics of both waves and particles, depending on how they are observed or measured.
The wave-particle duality arises from the mathematical framework of quantum mechanics, which describes the behavior of particles and their interactions. According to quantum mechanics, particles, including photons (particles of light), are described by wavefunctions that evolve according to specific equations, such as the Schrödinger equation.
When a quantum entity, such as a photon, is observed or measured, its wavefunction "collapses" into a specific state or outcome, which can be interpreted as a particle-like behavior. For example, in the double-slit experiment, individual photons are observed as localized particles when they interact with a screen. On the other hand, when light passes through the double slits without being observed, it exhibits wave-like interference patterns on a screen.
The wave-particle duality is not a contradiction but rather a reflection of the probabilistic nature of quantum mechanics. The behavior of quantum entities is described by wavefunctions, which contain information about the probability distribution of their properties. The wave-like and particle-like aspects are observed depending on the experimental setup and the type of measurement being performed.
Therefore, the wave-particle duality can be considered as a fundamental feature of quantum mechanics, describing the complex nature of quantum entities and the limitations of classical concepts when applied to the quantum realm.