The Fresnel Lens: the Invention That Saved 1000 Ships

[lorisarvendu]

Surely of interest to several members of this forum! The history and physics beyond that thing so many of us stick on top of our boxes.

And it's pronounced "Freh-nel".

https://www.youtube.com/watch?v=fQufI-QJLZg

 

[russellsuthern]

Interesting stuff!

Russell

 

[Volpone]

They use them in theater too, only in a "can" shape, with the lens at one end.  You have ellipsoidals that can be focused for specific effects and Fresnels for the more general lighting.