The behavior of subatomic particles, such as electrons and photons, exhibiting both particle-like and wave-like properties is a fundamental aspect of quantum mechanics. This dual behavior is often referred to as wave-particle duality. The wave-particle duality arises from the wave nature of matter and the probabilistic nature of quantum mechanics.
According to classical physics, particles are described as distinct entities with definite positions and velocities. However, at the quantum level, the behavior of particles is described by wave functions, which are mathematical functions that can exhibit wave-like characteristics, such as interference and diffraction.
The wave-particle duality is best illustrated by the famous double-slit experiment. In this experiment, when a beam of particles, such as electrons or photons, is directed at a barrier with two narrow slits, an interference pattern emerges on a screen behind the barrier, similar to what would be expected for waves passing through the slits. This interference pattern suggests that the particles exhibit wave-like behavior.
However, when detectors are placed to determine which path the particles take, the interference pattern disappears, and the particles behave more like distinct entities passing through one of the slits, akin to particles. The act of measurement or observation collapses the wave function, causing the particle to "choose" a definite position and behave like a particle.
The wave-particle duality is a fundamental concept in quantum mechanics and is not easily explained in classical terms. It suggests that subatomic particles do not possess classical properties such as definite positions and velocities until they are measured or observed. Instead, their behavior is described by a probability distribution given by the wave function. The wave-like and particle-like behavior of subatomic particles is complementary and depends on the experimental setup and the act of observation.