Three observable phenomena where particles exhibit wave-like behavior are:
Diffraction: Diffraction is the bending or spreading of waves as they encounter an obstacle or pass through a narrow opening. Surprisingly, particles such as electrons, protons, and even large molecules can also display diffraction patterns. This phenomenon was experimentally observed using diffraction gratings or double-slit setups. The fact that particles can exhibit interference patterns characteristic of waves indicates their wave-like nature.
Interference: Interference occurs when waves combine and either reinforce or cancel each other out. This phenomenon is not limited to classical waves but also applies to particles. For instance, in the double-slit experiment, particles like electrons or photons passing through two slits create an interference pattern on a screen, showing regions of constructive and destructive interference. The resulting pattern can only be explained by treating the particles as waves interfering with themselves.
Quantum Tunneling: Quantum tunneling is a quantum mechanical phenomenon where particles have a non-zero probability of crossing an energy barrier, even when classically they would not have enough energy to do so. This behavior is often explained by considering the wave-like nature of particles. According to quantum mechanics, particles can be described by a wave function that extends into regions where they are classically forbidden. The wave function allows particles to "tunnel" through energy barriers, appearing on the other side without going over the top.
These phenomena demonstrate that particles, at the quantum level, exhibit wave-like characteristics. They highlight the wave-particle duality of quantum mechanics, where particles can behave as both discrete particles and extended waves depending on the experimental context.