Arago spot

Rarity: Common

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At a glance

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Notion

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Science and technology

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What Wikipedia says

In optics, the Arago spot, Poisson spot, or Fresnel spot is a bright point that appears at the center of a circular object's shadow due to Fresnel diffraction. This spot played an important role in the discovery of the wave nature of light and is a common way to demonstrate that light behaves as a wave.

Excerpt from the Wikipedia article “Arago spot”, under the CC BY-SA 4.0 license. Read the article on Wikipedia

Image: Auteur inconnu, CC BY-SA 3.0, via Wikimedia Commons.