Found this at OpticalPoptitude.com

In physics, wave-particle duality holds that light and matter can exhibit properties of both waves and of particles. It is a central concept of quantum physics.

Through the work of Albert Einstein, Louis de Broglie and many others, it is now established that small objects, such as atoms, have both wave and particle nature, and that quantum mechanics provides the over-arching theory resolving this apparent paradox...........

Quantum Physics Double Slit Experiment - What The Bleep Movie