The double-slit experiment can be conducted with both waves and particles, including particles like electrons and photons. However, the results of the experiment differ depending on whether you're dealing with classical waves or quantum particles.
When the experiment is performed with classical waves, such as water waves or light waves, the waves pass through the two slits and interfere with each other, creating an interference pattern on the screen behind the slits. This pattern arises due to the constructive and destructive interference of the waves.
On the other hand, when the experiment is performed with particles, such as electrons or photons, it might seem counterintuitive, but they also exhibit wave-like behavior. This is known as wave-particle duality. The particles are sent through the double slits one by one, and over time, an interference pattern gradually emerges on the screen, resembling the pattern observed with classical waves.
The interference pattern observed in the double-slit experiment with particles arises from the wave nature of the particles. The particles, such as electrons or photons, have associated wavefunctions that describe their probabilities of being in different positions. These wavefunctions can interfere with each other, leading to the characteristic interference pattern on the screen.
However, when a measurement or observation is made to determine which slit a particle goes through, the interference pattern disappears. The act of measurement disturbs the wavefunction, collapsing it into a specific position, and the particle behaves more like a classical particle, appearing to go through one slit or the other.
In summary, the double-slit experiment can be performed with both waves and particles. The interference pattern arises from the wave nature of the particles, and the observation or measurement collapses the wavefunction, causing the particles to behave more like classical particles, thereby eliminating the interference pattern.