Fresnel lens

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Fresnellight

The extinction ratio is a parameter that quantifies the effectiveness with which a polarizer eliminates light polarization. It is particularly relevant in fields such as telecommunications, where polarization-dependent devices are common. The extinction ratio is computed by taking the ratio of the transmitted light intensity of the preferred polarization to the transmitted light intensity of the blocked polarization.

Knowing the extinction ratio of a polarizer provides insight into its performance in applications where the control of light polarization is critical. Accurate measurements and calculations of this ratio allow for better design and optimization of optical systems.

Fresnel lenses are still in operation today. According to the US Lighthouse Society, more than 75 Fresnel lenses are in use in American lighthouses, and businesses such as Dan Spinella’s Artworks Florida craft replicas that capture the beauty — and functionality — of the 19th-century breakthrough.

The most important part of a lighthouse might be one of the beautiful tools hidden inside of it: the Fresnel lens, a breakthrough that changed seafaring and saved lives.

As the above video shows, these lenses satisfied a need for lighthouses that could shine farther and through dense layers of fog. The Fresnel lens, invented by Augustin-Jean Fresnel, helped do that by capturing all the light coming from a lamp, then magnifying and steering it in one direction. Suddenly, lighthouses became more useful and shipwrecks diminished.