The photochromic lenses in transitional glasses contain silver halide molecules that temporarily change shape when exposed to ultraviolet light. This causes the lens to darken, and some of that light to be blocked.
One of the problems with them, however, is that the transition from clear to tinted can often take up to a few minutes. When you’re performing activities such as driving or even flying a plane, that’s simply not fast enough. Additionally, they won’t tint if you’re in a shaded place – such as the inside of a car – looking out onto a brightly-sunlit area.
By contrast, users of the Georgia Tech glasses can tint and un-tint them whenever and wherever they want, just by flipping a power switch.
via Gizmag
Image: American Chemical Society
