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Photochromism is the reversible change of color upon exposure to light. It is a transformation of a chemical species ( photoswitch ) between two forms by the absorption of electromagnetic radiation ( photoisomerization ), where the two forms have different absorption spectra.
A photochromic eyeglass lens, part of the lens darkened after exposure to sunlight while the other part remained covered. A photochromic lens is an optical lens that darkens on exposure to light of sufficiently high frequency, most commonly ultraviolet (UV) radiation.
Focal length of lens varies with the color of light Photographic example showing a high quality lens (top) compared to a lower quality one exhibiting transverse chromatic aberration (seen as a blur and a rainbow edge in areas of contrast)
The component S1 of the system, situated between the aperture stop and the object O, projects an image of the diaphragm, termed by Abbe the entrance pupil; the exit pupil is the image formed by the component S2, which is placed behind the aperture stop. All rays which issue from O and pass through the aperture stop also pass through the ...
The first camera lens with an inexpensive mass-produced molded glass aspheric element was the unnamed 12.5mm f/2.8 lens built into the Kodak Disc 4000, 6000 and 8000 (USA) cameras in 1982. It was said to be capable of resolving 250 lines per millimeter.
The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rubbery state as the temperature is increased. [2]
For the same reason sunglasses and filters were used by the American Army, especially for aviation, indeed Polaroid glasses were thought to protect aviator from sunlight but also atomic bomb explosions. [8] Cool-Ray was a division of American Optical for the sunglasses. It was the originator of the polarized sunglass as it is known today.
Oversized sunglasses, because of their larger frames and lenses, are useful for individuals who are trying to minimize the apparent size or arch of their nose. Oversized sunglasses also offer more protection from sunburn due to the larger areas of skin they cover, although sunblock should still be used.