Filter light

Three special tristimulus light filters are available which, when combined with a specific light source and a filter photometer, can be used to obtain color data (20). Although this method provides added precision and accuracy, it is seldom worth the extra effort required (see Color). 

Photochromic lenses for eyewear serve as variable density optical filters. Other appHcations for photochromic light filters have been proposed including gla2ing appHcations for solar attenuation, variable transmission camera lenses, and shields for protection against the light flash from a nuclear explosion. 

Besides the use of photochromic systems in light filters, their color development has also received considerable attention. For example, the introduction of photochromic components into product labels, tickets, credit cards, etc adds a mechanism for verification of authenticity (41,42). The active components are invisible until activated with an ultraviolet light source, after which they are easily detected. 

The principal features of an integral tri-pack are shown in Figure 8. The color records are stacked in the order shown, with the red record on the bottom, the green record next, and the blue record on the top. The blue record is on the top because it is necessary to interpose a blue light filter to remove... 

Slow yellow Blue light filter Fast magenta... 

Fig. 8 Transmittance of black light filter as a function of wavelength (A) and as a function of the length of operation at A = 254 and 365 nm (B)...

Light filters. Optical filters are used in colorimeters (absorptiometers) for isolating any desired spectral region. They consist of either thin films of gelatin containing different dyes or of coloured glass. 

Cobalt, sepn. of from nickel, (cm) 532 Codeine and morphine, D. of 740 Coefficient of variation 135 Colloidal state 418 See also Lyophilic, Lyophobic Colorimeters light filters for, 661 photoelectric, 645, 666 Colorimetric analysis 645 criteria for, 672 general remarks on, 645, 672 procedure, 675 solvent selection, 674 titration, 652... 

Light filters for colorimeters, see Filters, optical Limiting cathode potential 509 see also Controlled potential electro-analysis Linear regression 145 Lion intoximeter 747 Liquid amalgams applications of, 412 apparatus for reductions, 413 general discussion, 412 reductions with, (T) 413 zinc amalgam, 413 Liquid ion exchangers structure, 204 uses, 204, 560... 

Light Filtering and Antioxidant Properties of Macular Pigment.356... 

LIGHT FILTERING AND ANTIOXIDANT PROPERTIES OF MACULAR PIGMENT... 

Junghans, A., Sies, H., Stahl, W., 2001. Macular pigments lutein and zeaxanthin as blue light filters studied in liposomes. Arch Biochem Biophys. 391, 160-164. 

Thyroxine (57) was rapidly photodeiodinated by light filtered to give wavelengths above 300 nm. In the first few minutes the main product was 3,3, 5-triiodothyronine, but by 15 min, 3,5-diiodothyronine and 3-iodothyronine were present in major amounts. There were also traces of 3,3, 5-triiodothyronine and 3,3 -diiodothyronine. In some runs traces of 3,3, 5 -triiodothyronine and 3, 5 -diiodothyronine were detected. Over 30 min the main product was 3-iodothyronine. Further deiodination to thyronine was very slow, presumably because the UV spectra had lower-wavelength maxima as iodine was removed. Similar photolysis of 3,3, 5-triiodothyronine for 10 min also gave 3,5-diiodo-... 

In addition the light can be polarized so that only certain orientations of vibration of the light waves can be observed. Given suitable light filters the sculpture can discriminate (reflect, transmit) wavelengths even more sharply and so derive even more information. 

Another problem for the synthetic use of PFR is that the ortho-rearranged products may act as internal light filters, stopping the reaction. In synthetic routes leading to chromanones, chromones, and related compounds, this is of vital importance because the overall yield is limited by the photochemical step. Improved yields can be obtained if the a, 3-unsamrated orr/io-hydroxyphenones resulting from PFR are removed and cyclized to chromanones. This can be acomplished in one pot by irradiation in a two-phase system benzene/10% aqueous NaOH, whereby chromanones are directly obtained from phenyl crotonates in 80-90% yields [210]. 

Fig. 10.2 Schematic diagram of a reflected interference microscope 1 - tight source, 2 - heat reflecting filter, 3 - coUimator, 4 - diaphragm, 5 - light filter, 6 - photo film, 7 - projection ocular, 8 - semi-transparent silvered mirror, 9 - aperture diaphragm, 10- auxiliary lens, 11 - immersion lens, 12 - sample under investigation, 13 - substrate...

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