A couple of years ago there was some discussion of fresnel lenses. This kid came up with something that puts my fresnel to shame, in true Archimedes fashion:
More here:
Eric Jacqmain invented a 'Death ray' dish that had the intensity of 5,000 suns | Mail Online
More here:
Eric Jacqmain invented a 'Death ray' dish that had the intensity of 5,000 suns | Mail Online