In the context of the double-slit experiment, when electrons are directed towards the barrier with two slits, it is not accurate to say that electrons pass through one of the two slits in the same way a classical particle would. The behavior of electrons in the double-slit experiment is governed by quantum mechanics and exhibits wave-particle duality.
According to quantum mechanics, the state of a particle, such as an electron, is described by a probability wave or wavefunction. This wavefunction represents the probability distribution of where the electron is likely to be found upon measurement. When electrons are sent towards the double-slit apparatus, the wavefunction associated with each electron spreads out and passes through both slits simultaneously.
Importantly, the superposition of wavefunctions from the two slits gives rise to interference effects on the screen behind the slits, resulting in the characteristic interference pattern. This pattern demonstrates the wave-like nature of the electrons and is indicative of the probabilistic behavior of quantum particles.
Crucially, in the double-slit experiment, when the electrons are not observed or measured to determine which slit they pass through, the interference pattern is preserved. This implies that the electrons do not behave as classical particles that must choose one slit or the other. Instead, they exhibit wave-like behavior and interfere with themselves, leading to the pattern on the screen.
The inability to determine through which specific slit an electron passes without disturbing its wavefunction is a manifestation of the famous measurement problem in quantum mechanics. The act of measurement or observation collapses the electron's wavefunction to a specific state, forcing it to behave more like a classical particle with a definite location.
In summary, electrons in the double-slit experiment do not pass through only one of the two slits in a classical particle sense. Their behavior is best described by a superposition of wavefunctions, exhibiting both particle and wave-like characteristics, until they are measured or observed, at which point their wavefunctions collapse to specific states.