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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.
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. [1]
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)
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.
Dr. Dinesh Prasad Saklani is the director of NCERT since 2022. [2] In 2023, NCERT constituted a 19-member committee, including author and Infosys Foundation chair Sudha Murthy, singer Shankar Mahadevan, and Manjul Bhargava to finalize the curriculum, textbooks and learning material for classes 3 to 12. [4]
The Helmholtz reciprocity principle describes how a ray of light and its reverse ray encounter matched optical adventures, such as reflections, refractions, and absorptions in a passive medium, or at an interface.
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.