How do photochromic lenses respond to increased sunlight exposure?

Photochromic lenses are designed to dynamically adjust their tint based on the intensity of UV light they are exposed to. When exposed to increased sunlight, particularly ultraviolet (UV) rays, these lenses undergo a chemical reaction that causes them to darken. This darkening effect helps protect the eyes from harmful UV radiation and reduces glare, making it more comfortable to see in bright conditions.

In lower light conditions or indoors, the absence of UV exposure allows the photochromic lenses to gradually return to their clear state. The ability to automatically adjust their tint makes them a convenient choice for wearers who frequently transition between varying light environments. This unique property is vital for achieving optimal visual comfort and protection in different lighting conditions. The other options do not accurately describe the behavior of photochromic lenses when subjected to sunlight.