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# Wave-particle duality

## Wave-particle duality

One of the fundamental concepts in quantum physics is the wave-particle duality exhibited by all matter. At quantum scales, waves are observed to behave like particles and particles like waves.

The photoelectric effect is an example of how a wave (electromagnetic radiation) behaves like a stream of particles (photons) when interacting with metals.

Similarly, a beam of electrons (a group of particles) exhibits diffraction (normally only exhibited by waves) after passing through a grating.

The French scientist Louis-Victor de Broglie (pronounced as "broy") introduced the notion that all particles have a wavelength (a characteristic of waves) and equivalently, all photons (which are components of waves) have a corresponding momentum (a characteristic of particles).

This is given by the de Broglie relation: $$\lambda=\frac{h}{p}$$ $\lambda$ is the wavelength of the particle/photon, $h$ is the Planck constant and $p$ is the momentum of the particle/photon.