Photons, which are the fundamental particles of light, exhibit properties of both particles and waves. This duality is one of the central principles of quantum mechanics.
When photons are observed in certain experiments, they behave like particles. For example, in the photoelectric effect, photons can knock electrons out of a material, which is consistent with a particle-like behavior.
On the other hand, photons also exhibit wave-like behavior in phenomena such as interference and diffraction. In these cases, light waves can interfere with each other constructively or destructively, producing patterns of light and dark regions. This behavior is similar to what is observed with other wave phenomena, such as water waves or sound waves.
The wave-particle duality of photons (and other quantum entities) arises from the wave nature of their underlying quantum wavefunctions and their interactions with the environment. According to quantum mechanics, particles are described by wavefunctions, and the behavior of particles is determined by the wavefunction's properties.
The specific behavior observed in a given experiment depends on the nature of the interaction and the measurement being performed. The wave-particle duality of photons reflects the fundamental nature of quantum entities, which can exhibit both particle-like and wave-like characteristics depending on the experimental context.
It's important to note that the wave-particle duality is not a change in the nature of photons themselves but rather a reflection of how they are observed and measured. The behavior of photons is inherently probabilistic and can only be described in terms of probabilities and wavefunctions in the framework of quantum mechanics.