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Polarizing sheets are used in liquid-crystal displays, optical microscopes and sunglasses.Since Polaroid sheet is dichroic, it will absorb impinging light of one plane of polarization, so sunglasses will reduce the partially polarized light reflected from level surfaces such as windows and sheets of water, for example.
Herapathite, or iodoquinine sulfate, is a chemical compound whose crystals are dichroic and thus can be used for polarizing light. It was discovered in 1852 [1] by William Bird Herapath, a Bristol surgeon and chemist. One of his pupils found that adding iodine to the urine of a dog that had been fed quinine produced unusual green
Pasteur noticed that crystals of this compound come in two asymmetric forms that are mirror images of one another. Sorting the crystals by hand gave two forms of the compound: Solutions of one form rotate polarized light clockwise, while the other form rotate light counterclockwise. An equal mix of the two has no polarizing effect on light.
However, this crystal is seldom used as a polarizer, since the dichroic effect is strongly wavelength dependent and the crystal appears coloured. Herapathite is also dichroic, and is not strongly coloured, but is difficult to grow in large crystals. A Polaroid polarizing filter functions similarly on an atomic scale to the wire-grid polarizer ...
The original meaning of dichroic, from the Greek dikhroos, two-coloured, refers to any optical device which can split a beam of light into two beams with differing wavelengths. Such devices include mirrors and filters , usually treated with optical coatings , which are designed to reflect light over a certain range of wavelengths and transmit ...
The primary causes include post-cataract surgery, certain medications, and, less commonly, neurological or ophthalmological conditions. Post-cataract surgery is a common cause, as replacing the natural lens with a synthetic one increases exposure to blue light, leading to temporary blue-tinted vision. This effect usually resolves as the eye adapts.
Additionally, nicotine can cause constriction of the blood vessels, reducing blood flow to the eyes and making them more vulnerable to damage and disease. [30] It is recommended that smokers exhibiting signs and symptoms of retinopathy engage in smoking cessation to improve their quality of life.
Slit-lamp photographs of three-year-old patient with nephropathic cystinosis before (left) and after (right) cysteamine eyedrop therapy. The drops dissolve the crystals in the cornea. By about age two, cystine crystals may also be present in the cornea. The buildup of these crystals in the eye causes an increased sensitivity to light ...