Jim:
By coincidence, I just opened Saturday’s post to find the link to the Fresnel lens YouTube video. What are the odds? On Friday I went yard sale shopping. (A rare day of freedom for me since I normally work that day. We are down for two weeks for factory work and in preparation of the new potato crop.) At this sale was the Fresnel lens from a scrapped out projection television set on the front lawn. It was leaning up and in the open. I told the lady that is not a good idea an explained to her the concept of the physics and that they draw light and concentrate the energy just like a magnifying glass does. It is very dry here in southwestern Idaho and Eastern Oregon and many burn bans are in affect.
This lens had come from the front screen of a scrapped out projection television set. Also at this sale sitting on the same table were the three color tubes. In case anyone is interested, there are some awesome high quality large glass magnifying lenses inside these color projection tubes. I have several from such and they are worth having. By the way, Fresnel a French word and its pronounced “Fra-Nall”. Regards, – RBS