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Understanding Surface Films: GLASS, Nonreflecting. When light strikes a plate of glass not all of it is transmitted. At each surface a small portion is reflected. These reflections decrease the amount of transmitted light and can give rise to glare. A glass surface may be treated to reduce its reflection losses. Strictly nonreflecting glass is possible only under very special conditions but the term is sometimes used loosely for any glass with treated surfaces. Plastics and crystals may be treated as well. Treated lenses and other optical elements are referred to as coated optics. The reflection reducing effect depends on the interference of light in surface films developed by the method of treatment. Such films are variously known as reflection-reducing, antireflection or transmission films.
Harm's fame rests largely on al-Maqamat (The Sessions; that is, literary recitals), comprising 50 episodic essays about a rogue and his serious foil. Its display of learning and elaborate style, peculiarly appropriate to both the Arabic language and the script, are even more impressive than Harm's narrative ingenuity and shrewd social comment. The prototype of this genre, by al-Hamadhani (died 1008), may seem superior, but it was Hariri's work that influenced Islamic taste for several centuries. Even in Arabic, commentaries were required to elucidate the allusions and preciosities. Yet this was one of the earliest literary works to catch Western attention; laborious translations have been published since the 17th century.
HARKINS, William Draper (1873-1951), American chemist, who contributed to the understanding of surface films, polymerization, and atomic structure. His interest in surface chemistry led to an understanding surface films of mono-molecular films on liquid surfaces and the orientation of molecules therein. His study of soap micelles was important to his work on emulsion polymerization in rubber synthesis. In nuclear chemistry he worked on the abundance and stability of elements, the conversion of hydrogen to helium as a source of stellar energy, and the concept of the intermediate nucleus in transmutation. He separated the isotopes of chlorine in 1920 and, later, the isotopes of mercury.
It is because of the varying effects these light rays have upon our eyes and upon photographic films that color filters are helpful and necessary in picture making. Note, however, that they are useful only in black-and-white photography. They do not result in getting pictures in natural colors.
For general photography the infrared rays can be disregarded (except for cutting out haze in long-distance photography, and for unusual effects) because ordinary and even panchromatic films are not affected by them. On the other hand the ultraviolet rays have a very marked effect upon all films. |
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