Bonjour y'all! Laissez le bon Trump rouler!!!
Know your Nautical terminology
Fresnel lens
The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. A Fresnel lens can capture more oblique light from a light source, thus allowing the light from a lighthouse equipped with one to be visible over greater distances. It has been called "the invention that saved a million ships."
1: Cross section of a spherical Fresnel lens 2: Cross section of a conventional spherical plano-convex lens of equivalent power
The running lights on ships are almost exclusively Fresnel lenses.
WWG1WGA
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)
Thank you for the post about the Fresnel lens.
When engineering is both practical and beautiful, I almost want to cry. With joy.
Look at the Golden Gate Bridge, for example.
If you have not visited in person a lighthouse with a Fresnel lens (functioning or not), I urge you to do so. A working Fresnel lens is more beautiful than any chandelier.
In fact, the docent at one of the lighthouses I toured did call it a “chandelier.” < smile >
Story about the inventor (Augustin Fresnel), here:
https://www.smithsonianmag.com/science-nature/science-makes-a-better-lighthouse-lens-170677431/
As a child, he was a slow learner who showed little interest in language studies or in tests of memory. By the age of 8, he could barely read. Yet his boyhood friends, for whom he studiously determined how to increase the power of popguns and bows, called him “the genius.” When applied to optics, his genius proved to be real and considerable. Where others had improved existing lighthouse technology, Fresnel leapt forward by studying the behavior of light itself. His studies both advanced the understanding of the nature of light and produced the most important breakthrough in lighthouse lights in 2,000 years.
Fresnel worked out a number of formulas to calculate the way light changes direction, or refracts, while passing through glass prisms. Working with some of the most advanced glassmakers of the day, he produced a combination of prism shapes that together made up a lens. The Fresnel lighthouse lens used a large lamp at the focal plane as its light source. It also contained a central panel of magnifying glasses surrounded above and below by concentric rings of prisms and mirrors, all angled to gather light, intensify it and project it outward.