The understanding of light as both particles and waves is a fundamental concept in physics and is explained by the theory of quantum mechanics.
According to classical physics, light was considered to be a wave phenomenon. This wave model successfully explained many properties of light, such as interference, diffraction, and polarization. However, in the late 19th and early 20th centuries, experiments, such as the photoelectric effect and the Compton effect, could not be explained solely by the wave nature of light.
To resolve these inconsistencies, Albert Einstein proposed in 1905 that light could also exhibit particle-like behavior. He suggested that light consists of discrete packets of energy called photons. These photons were treated as particles with specific energies and momenta.
The wave-particle duality of light was further developed by quantum mechanics, which is the branch of physics that describes the behavior of particles at the microscopic level. According to quantum mechanics, particles, including photons, exhibit wave-like properties and can behave both as particles and waves depending on the experimental setup or observation.
The wave-particle duality is not unique to light. It applies to other particles as well, such as electrons and atoms, although the specific manifestations of this duality can vary. The behavior of particles is described by wavefunctions, which are mathematical entities that represent the probability distribution of finding a particle at a particular location or with a specific energy.
In experiments, light can exhibit wave-like behavior, such as interference and diffraction patterns, where it shows characteristics of waves interacting with each other. At the same time, light can also display particle-like behavior, as observed in phenomena like the photoelectric effect, where individual photons transfer their energy to electrons.
The wave-particle duality of light is a fundamental aspect of quantum mechanics and is deeply rooted in the mathematical formalism of the theory. It is important to note that our understanding of the behavior of light and other particles is based on mathematical models and experimental observations, which allow us to describe and predict their properties and interactions, even though the underlying mechanisms might not always be intuitive.