The two-slit experiment is a fundamental experiment in quantum mechanics that provides compelling evidence for the wave-particle duality of particles, such as electrons or photons (particles of light). It reveals the wave-like behavior of particles and demonstrates the interference phenomenon associated with waves.
In the two-slit experiment, a beam of particles, like electrons, is directed towards a barrier that contains two narrow slits. Behind the barrier, there is a screen that detects the particles. If particles behaved purely like classical particles, one would expect them to pass through either one of the slits and hit the screen, creating two distinct regions of impact aligned with the slits.
However, what is observed is quite different. When particles are sent one by one through the slits, they do not simply create two distinct regions on the screen. Instead, they produce an interference pattern consisting of alternating bands of bright and dark regions.
This interference pattern is a characteristic of waves, not particles. It occurs when waves interact with each other and their crests and troughs either reinforce or cancel each other out. In the case of the two-slit experiment, the particle's wave-like nature leads to an interference pattern because the waves associated with the particles passing through the two slits interfere with each other.
This phenomenon suggests that the particles, even when sent individually, exhibit wave-like properties and interfere with themselves. It implies that each particle simultaneously passes through both slits and interferes with its own wave function. The resulting pattern on the screen is the accumulation of these interference effects, indicating that particles can exhibit wave-like behavior.
The two-slit experiment is a powerful illustration of wave-particle duality because it shows that particles possess both particle-like and wave-like characteristics simultaneously. The experiment highlights the non-intuitive nature of quantum mechanics, where particles can exhibit behaviors that are not easily explained using classical physics concepts alone.