In a recent post about Maine lighthouses, I included two photos of the Fresnel lenses used to project the bright light beam across the water. One of the readers is a man I’ve enjoyed working with before in the blog world. He suggested I add a post with some description of how the Fresnel lens works. Here it is.
Basics of Converging Lenses
The converging, or convex lens, is able to bring parallel rays of light toward a focal point. As a child, I played with a magnifying glass lens to burn leaves, grass, and other things.
The lens can also be used in a different way to project light rays parallel to each other in a beam. Simple projectors work on this basic principle. A lighthouse is designed to do this.
Large Lens Applications
A problem arises when the optical instrument using a convex lens becomes very large. The…
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