Lenses achromatic

Lead oxide is used in producing fine "crystal glass" and "flint glass" of a high index of refraction for achromatic lenses. The nitrate and the acetate are soluble salts. Lead salts such as lead arsenate have been used as insecticides, but their use in recent years has been practically eliminated in favor of less harmful organic compounds. 

Microscopists were not entirely idle, however, and after Giovanni Battista Amici (1786-1863) introduced achromatic lenses in France in 1827, the cell theory was not far behind. Henri Dutrochet (1776-1847) had already proposed that animal and plant tissues were constituted of cells, a view reiterated by many, notably Jan Evangelista Purkyne (1787-1869), Johannes Muller (1801 -1858), andjacob Henle (1809-1885). Felix Dujardin... 

While the Abbe number is important in certain specialized applications such as the design of achromatic lenses which focus a range of wavelengths to the same spot, the variation of n with the wavelength of visible light is normally quite small, and will not be discussed further. 

Although Bacon has been described as a physician rather than a chemist, we are indebted to him for many scientific discoveries. He was almost the only astronomer of his time and in this capacity rectified the Julian calendar which, although submitted to Pope Clement IV in 1267, was not put into practice until a later Papacy. He was responsible also for the physical analysis of convex glasses and lenses, the invention of spectacles and achromatic lenses, and if not for the actual constmction, at any rate for the theory of the telescope. As a student of chemistry he called attention to the chemical role played by air in combustion, and having carefully studied the properties of saltpetre, taught its purification by dissolution in water and by crystallisation. 

FIGURE 45.9 Schematic of a confocal LIP detection system with source, optics, and detector shown. The optics include mirrors (M), laser line filter (LF), half-wave plate (X/2), polarizer (pol), dichroic beamsplitter (DB), microscope objective (MO), pinhole (ph), filter, and achromat lenses (achr). The source shown is an argon ion laser, and the detector is an avalanche photodiode (APD). While the electrophoresis channel shown here is in a capillary (CE), the system could be readily applied to a microchip. (Reprinted from Johnson, M.E. and Landers, J.P., Electrophoresis, 25, 3515, 2004. With permission.)... 

Over the next three hundred years, optical telescopes underwent vast technological improvements. For example, achromatic lenses were invented to compensate for the errors in color caused by older lenses that foiled to treat all the colors of visible light in the same way. Radio telescopes were first developed in the twentieth century, based on the discovery that faraway celestial bodies were constantly emitting faint amounts of radiation in the form of radio waves. This new form of telescopy was soon applied to both military radar operations and astronomical research. 

Various types of lasers can be linked to the microscope [72], but up to now only continoiis-wave gas lasers have been used routinely. This includes argon-ion lasers having excitation lines at 488 and. 14 nm and helium-neon lasers with a major line at 633 nm and a weaker line at 543 nm. The use of UV lasers requires achromatic lenses and. specifically designed scanning mirrors. Lasers... 

If achromatic lenses (which are expensive in the infrared and ultraviolet region) are not employed, the focal length of the two lenses decreases with the wavelength. This can be partly compensated by inclining the plane... 

The early telescopes depended solely upon the refractive power of curved transparent glass lenses to redirect the light. In general, these telescopes were plagued by chromatic aberration (rainbow images) until the invention in 1752 of achromatic lenses, which are still used today in improved forms. Curved reflective surfaces (i.e., mirrors) were developed after refractors but were not as useful until highly reflective metal coatings could be applied onto... 

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