Welcome to brain Stuff from house stuff works dot com where smart happens. Hi. I'm Marshall Brain with today's question, how does a Frenelle lens work? If you've ever looked at the lens of a normal magnifying glass, you know that it's thick in the middle and it tapers down to next to nothing at the edges. In other words, it's shaped like a lentil, which is where the word lens comes from. It would not be very easy to make a giant magnifying glass lens because it would be thick, heavy,
and hard to mount. The thin piece of plastic called a Fernell lens solve this problem. It's flat on one side and ridged on the other, and very thin across the whole surface. For Nell lenses were first used in the eighteen hundreds as the lens that focuses the beam and lighthouse lamps. Plastic for Nell lenses are used as magnifiers when a thin light lens is needed. The quality of the image isn't nearly as good as that from a continuous glass lens, but in lots of applications like
a lighthouse, perfect image quality isn't necessary. The basic idea behind a for Nell lens is simple. Imagine taking a plastic magnifying glass lens and slicing it into a hundred concentric rings, like the rings of a tree. Each ring is slightly thinner than the next and focuses the light towards the center. Now take each ring, modify it so it's flat on one side, and make it the same thickness as the others to retain the rings ability to focus the light towards the center. The angle of each
rings angled face will be different. Now, if you stack all the rings back together, you have a Fornell lens. You can make the lens extremely large if you like. Large for Nell lenses are often used as solar concentrators. For more on this and thousands of other topics. Because house stof works dot com