FRESNEL LIGHTHOUSE LENS
As maritime travel and commerce increased in the 1800s, so did the quantity and quality of navigational lights in lighthouses. One of the greatest improvements in the technology came in 1822 when a French physicist named Augustin Jean Fresnel (Freh-nel) introduced a new revolutionary lens design that would change lighthouse optics forever, making waterways safer for sailors worldwide. His invention improved lighthouse lights in several ways including brightness, distance, recognition & efficiency.
“Because of these technical advancements, it is easy to overlook the beauty of the lens itself. It is truly a work of art. Most Fresnel lenses contain hundreds of glass prisms which were painstakingly ground, cut, and polished. They sparkle like jewels when lit at night.”
… “Fresnel’s lens resembles a giant beehive with a complex system of multi-faceted glass prisms mounted in a brass framework. The prisms reflect and refract (bend) light and magnify it, thereby taking rays of light that would normally scatter in all directions and focusing them into a single beam. Because of this design, a Fresnel lens is much more efficient than traditional light sources. Tests show that an open flame loses nearly 97% of its light. A light with a reflector placed behind it loses 60-80% of its light. A Fresnel lens, however, loses a maximum of 20% of its light. This concentrated light of Fresnel’s lens vastly improved lighthouse effectiveness. Before its invention, the brightest lighthouse beams could only be seen from 8-12 miles away. The light from a Fresnel lens could shine all the way to the horizon, more than 20 miles away.”
--excerpts from (nps.gov)