In the double-slit experiment, the wave behavior of particles can be observed even when using single particles, such as electrons or photons. The interference pattern that emerges on the screen behind the double slits is a characteristic of wave behavior and demonstrates the wave-particle duality of quantum particles.
The disappearance of the interference pattern and the emergence of classical particle-like behavior typically occur when the de Broglie wavelength of the particles becomes small compared to the experimental setup. The de Broglie wavelength, denoted by λ, is related to the momentum of the particle. For a particle with momentum p, the de Broglie wavelength is given by λ = h/p, where h is the Planck's constant.
As the mass and momentum of a particle increase, its associated de Broglie wavelength becomes smaller. When the de Broglie wavelength becomes comparable to the size of the slits or the spacing between them, the interference pattern becomes less pronounced or disappears.
For macroscopic objects, such as baseballs or everyday objects, the de Broglie wavelength is incredibly small and practically undetectable in typical laboratory conditions. Hence, for objects of macroscopic size, the wave behavior is not observable in the double-slit experiment.
On the other hand, for subatomic particles like electrons or photons, which have very small masses and can exhibit wave-like behavior, the interference pattern is readily observable even when considering individual particles. The wave-particle duality is a fundamental characteristic of quantum mechanics and is not limited to specific particle sizes but applies to all quantum particles.