Interference pattern which stands a proof of Wave particle duality in the Double slit experiment
Wave–particle duality is not confined to light, however. Everything exhibits wave-particle duality, everything from electrons to baseballs.
The behavior of relatively large objects, like baseballs, is dominated by their particle nature; to explain the behavior of very small things like electrons, both the wave properties and particle properties have to be considered.
When light falls on narrow slits, it behaves as only a wave. Under other conditions, such as when it falls on a metal, it behaves just as particle. This multiple personality of light is referred to as "wave–particle duality". Light behaves as a wave, or particle, depending on its observation. It's wave–particle duality lies at the heart of the Heisenberg uncertainty principle.
Particle nature of light is suggested to explain the photoelectric effect. It was observed that shining a light on certain metals would lead to an electric current in a circuit.
If a photon of light is absorbed by the electron, the electron gains potential energy and raises to a higher energy level. The electron's higher position is only momentary as a photon of light is emitted by the electron at the same instant. The electron loses potential energy returns to a lower level as it emits radiant energy.