wave-particle duality

The exhibition of both wavelike and particlelike properties by a single entity, as of both diffraction and linear propagation by light.

The concept that waves carrying energy may have a corpuscular aspect and that particles may have a wave aspect; which of the two models is the more appropriate will depend on the properties the model is seeking to explain. For example, waves of electromagnetic radiation need to be visualized as particles, called photons, to explain the photoelectric effect while electrons need to be thought of as de Broglie waves in electron diffraction.

The inherent contradiction in the way energy behaves. At the turn of the 20th century, it was believed that light was electromagnetic waves and electrons were particles. By the 1930s, it was determined that light behaves as if it were made up of particles (photons) as well as waves, and electrons also behave like waves. This has driven scientists to drink and is one of the most puzzling phenomena in the universe. See quantum mechanics.

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For more information on wave-particle duality, visit Britannica.com.

In quantum mechanics, the condition that allows every quantum to appear like a wave in some experiments and like an elementary particle in others.