How Auto Darkening Lenses Work
Arthur C. Clark famously said that any sufficiently advanced technology is indistinguishable from magic. That certainly applies to face shields, goggles, and glasses that automatically darken. That sorcery has existed for decades, but it has been refined and is more widely available now than ever. This change of lens shade as light increases is called photochromism, and it depends on a reversible chemical reaction that takes place when a material embedded in glass or plastic is exposed to certain wavelengths of light....