The concept you're referring to is known as wave-particle duality, which is a fundamental principle in quantum mechanics. It states that particles, such as electrons or photons, can exhibit both wave-like and particle-like behavior depending on the experimental setup.
Wave-particle duality was first proposed by Louis de Broglie and later confirmed through experiments like the double-slit experiment. Here's a simplified explanation of how it works:
Wave-like behavior: When particles are not being observed or measured, they can exhibit wave-like properties. This is described by a mathematical function called a wavefunction, which describes the probability distribution of finding the particle at different positions in space. The wavefunction can interfere with itself, leading to phenomena like diffraction and interference, similar to what we observe with classical waves.
Particle-like behavior: When a particle is measured or observed, it manifests as a localized particle with a definite position. The act of measurement "collapses" the wavefunction, and the particle is found in a specific position. This is often referred to as the "collapse of the wavefunction."
Uncertainty principle: One of the key implications of wave-particle duality is the Heisenberg uncertainty principle, which states that there is a fundamental limit to the precision with which certain pairs of physical properties, such as position and momentum, can be known simultaneously. This means that the more precisely we try to measure one property (e.g., position), the less precisely we can know the other property (e.g., momentum).
So, while it may seem counterintuitive, particles in the quantum world can exhibit wave-like properties and exist in a superposition of different states until measured, at which point they behave more like localized particles. The exact nature of this duality is still a subject of ongoing research and philosophical debates in quantum mechanics.