According to quantum mechanics, particles can exhibit wave-particle duality, which means they can exhibit characteristics of both particles and waves. This duality was first proposed by Louis de Broglie and later supported by experimental evidence such as the double-slit experiment.
The behavior of particles at the quantum level is described by wave functions, which are mathematical functions that represent the probability distribution of finding a particle in a particular state. The wave function describes the wave-like behavior of the particle, including properties such as interference and diffraction, similar to classical waves.
However, when we observe or measure a particle, its wave function collapses to a specific value, and we perceive it as a localized particle at that moment. This collapse is often referred to as the "measurement problem" in quantum mechanics. The act of measurement or observation forces the particle to "choose" a specific state or location.
The reason we usually perceive objects as either particles or waves, rather than both simultaneously, is that macroscopic objects, such as everyday objects, have large masses and interact strongly with their environment. These interactions cause the quantum behavior to "decohere" and become less apparent at the macroscopic scale. As a result, the wave-like properties become negligible, and we typically observe the object as a classical particle.
On the other hand, at the microscopic scale, such as with electrons or photons, the wave-particle duality is more pronounced because the mass is much smaller, and interactions with the environment are less significant. This allows the wave-like behavior to manifest and be observable in certain experiments.
In summary, while objects can exhibit both particle-like and wave-like properties, the specific manifestation depends on the scale and the experimental conditions. At the macroscopic scale, classical behavior dominates, and objects are perceived as particles. At the microscopic scale, quantum behavior becomes more apparent, and objects can exhibit wave-like properties.