The behavior of particles, including electrons, is described by quantum mechanics, which introduces a wave-particle duality. This duality means that particles can exhibit both wave-like and particle-like behavior, depending on the experimental setup and the observations made.
In the case of the two-slit experiment, which is a fundamental experiment in quantum mechanics, electrons are fired one at a time towards a barrier with two slits. Behind the barrier, a screen records the pattern of electron hits. Surprisingly, even when electrons are sent individually, an interference pattern emerges on the screen, characteristic of wave-like behavior.
The explanation lies in the wave-particle duality of quantum mechanics. Before being detected, the electron is described by a wave function, which is a mathematical entity that contains information about the probability distribution of finding the electron at different positions. The wave function evolves according to the Schrödinger equation, and its behavior can exhibit interference effects, similar to how waves in classical physics can interfere.
When an electron passes through the two slits, its wave function spreads out and can interfere with itself. This interference leads to the observed pattern on the screen. However, upon detection, the electron's wave function "collapses" to a specific location, and the electron is detected as a localized particle at a particular point on the screen.
In essence, the electron's behavior as a wave is not contradictory to its localized nature when observed. The wave-like behavior is manifested in the probabilistic distribution of detections on the screen, while the particle-like behavior is observed when a specific location is measured.
It's important to note that the wave-particle duality is a fundamental aspect of quantum mechanics and applies not only to electrons but also to other particles, such as photons. It is a profound and still actively studied aspect of quantum physics that challenges our classical intuitions about the nature of matter and energy.