IN this communication I give a somewhat more general discussion of the Fresnel drag coefficient than is usual, with the view of clarifying the relation between two expressions for it, which occur ...

Making a glass Fresnel lens with its concentric rings requires even more work, but as the ever-resourceful [Robert Murray-Smith] shows us, a Fresnel lens can be made from far more mundane materials.

If you are a Hackaday reader, you probably know what a Fresnel lens is. You find them in everything from overhead projectors to VR headsets. While it seems commonplace now, the Fresnel lens was an ...