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Lighthouse Glossary

Fresnel Lens: (fruh-nell lens) A thin optical lens consisting of concentric rings of segmental lenses and having a short focal length, used primarily in spotlights, overhead projectors, and the headlights of motor vehicles. [Editor: and, of course, lighthouse lights!]

Source: The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2000 by Houghton Mifflin Company.

The Fresnel lens was designed in 1822 by a French Physicist named Augustine Fresnel. The Fresnel Lens system includes six lens sizes, ranging from the sixth up to the first. The prisms of the lenses bend light so that it can shine much further than just a regular light.


Shoal: 1) A shallow place in a body of water. 2) A sandy elevation of the bottom of a body of water, constituting a hazard to navigation; a sandbank or sandbar.

Source: The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2000 by Houghton Mifflin Company.




















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