Sunglasses, also known as sunglasses, are an instrument to protect the eyes, mainly to prevent excessive exposure of visible light and some ultraviolet and infrared rays.

The history of sunglasses can be traced back to18th century, when people began to use colored glasses to prevent injuries during the processing of wood and leather. /kloc-in the 0/9th century, as the intensity of sunlight was gradually recognized by people, people began to realize the protective effect of sunglasses on their eyes.

Modern sunglasses design has been very diverse, and there are many choices in color, frame shape, material and lens design. When choosing sunglasses, people usually need to consider many factors, such as the color and filtering effect of sunglasses, whether they can block ultraviolet rays and whether they are suitable for different occasions.

The color and filtering effect of sunglasses are important factors that affect the visual experience. Generally speaking, dark sunglasses can filter light better, while light sunglasses can provide a clearer visual experience. In addition, sunglasses of different colors can be suitable for different occasions and clothes.

Photo gray glasses

The lenses of color-changing glasses will darken after the arrival of sunlight. When the light dimmed, it brightened again. This is possible because silver halide crystals are at work. Under normal circumstances, it can keep the lens completely transparent. Under the irradiation of sunlight, the silver in the crystal is separated.

Free silver forms small aggregates in the lens. These small syndicates are jagged irregular blocks. They can't transmit light, but can only absorb light. As a result, the lens darkens. In the case of dark light, the crystal re-forms and the lens returns to a bright state.