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What Is a Fresnel Lens?

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Quick Answer

A Fresnel lens is a flat, lightweight lens made of concentric ridged sections that focus light as effectively as a much thicker conventional lens.

The Full Story

Invented by Augustin-Jean Fresnel in 1822, the Fresnel lens replaces the curved bulk of a conventional lens with concentric stepped rings, each angled to refract light to a common focal point. This reduces thickness and weight while maintaining optical power. Fresnel originally developed it for lighthouses. The Fresnel lens in the Makapuu Point Lighthouse in Hawaii is 2.5 metres tall and contains over 1,000 individual prism rings. Today, Fresnel lenses are used in overhead projectors, solar concentrators, and VR headsets.

Key Facts

1.Before Fresnel lenses, lighthouses used mirrors that wasted most of the light — Fresnel lenses captured about 85%.
2.Augustin-Jean Fresnel died at just 39 but revolutionised both optics and lighthouse engineering.
3.Large Fresnel lenses for lighthouses were classified into orders — a first-order lens stood about 2.6 metres tall.

YouTube Angle

Suggested video title for this topic:

"The Lens That Saved Ships — How Fresnel Lenses Focus Light"