The concept of wave propagation through a barrier in quantum mechanics does not imply that individual particles themselves are physically traversing the barrier. Instead, it refers to the behavior of the wave function associated with the particles.
In quantum mechanics, particles are described by wave functions that evolve over time according to Schrödinger's equation or other appropriate equations. These wave functions represent the probability amplitudes associated with different possible states of the particles. When a wave function encounters a barrier, such as in the case of a particle encountering a potential energy barrier, it undergoes a process called tunneling.
Tunneling allows the wave function to extend into classically forbidden regions, meaning that there is a finite probability for the particle to be found on the other side of the barrier, even though it classically lacks the necessary energy to cross the barrier. This behavior is a result of the wave-like nature of particles in quantum mechanics.
Experimental evidence for wave function propagation through barriers is obtained through observations of phenomena like quantum tunneling or interference patterns. For example, in the case of electron tunneling, experiments have been conducted to measure the probability of electrons passing through a potential barrier. The observed tunneling probabilities match the predictions made by quantum mechanics, which assumes wave-like behavior.
It's important to note that while we cannot track the path of individual particles or determine which specific particle passed through the barrier, the statistical behavior of an ensemble of particles is consistent with the predictions of quantum mechanics. Through careful experimentation and analysis, physicists are able to infer the wave-like behavior and the propagation of wave functions through barriers based on the observed outcomes and statistical patterns.