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Topic: Light absorption

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absorption spectroscopy

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	Method for photometric measurement of light absorption of liquid samples in cuvettes - Patent 4549809
		In the method of the invention, measurements are taken of the light absorption of the cuvette and its contents at precisely timed intervals as the cuvette passes through the light beam at a predetermined rate of motion.
		It has been found that by using the measurement of light absorption at the same point along the path of movement as to each cuvette, the errors due to variations in the light absorption of the glass, or the materials, in the walls of the cuvette are unexpectedly reduced.
		At block 57, the light absorptions and from that the optical density value corresponding to a specific position, such as the central portion of the cuvette, is calculated from data Y(I) and Y(J) whose subscripts are I, and J, respectively.
	www.freepatentsonline.com /4549809.html (2475 words)

	ABSORPTION OF LIGHT - Online Information article about ABSORPTION OF LIGHT
		call j, which is the proportion absorbed in one centimetre, the "coefficient of absorption" of the medium.
		It is better then to define the coefficient of absorption as a quantity k such that k/n of the light is absorbed in 1/nth part of a centimetre, where n may be taken to be a very large number.
		In the case of solutions, if the absorption of the solvent is negligible, the effect of in-creasing the concentration of the absorbing solute is the same as that of increasing the thickness in the same ratio.
	encyclopedia.jrank.org /A10_ADA/ABSORPTION_OF_LIGHT.html (1712 words)

	New Developments in Color Therapy: Acupuncture Meridians Facilitate the Body's Absorption of Light
		Colored light has a particular ability to balance the autonomic nervous system, which is crucial in most chronic and functional disorders as it regulates all of the automatic processes of the human body: breathing, the beating of the heart, the functioning of the digestive tract, the stress response.
		Light from the hypothalamus is then sent to the pineal gland, the body's light meter and only gland in the body not controlled by higher neurological centers.
		So the light emitted from a full spectrum fluorescent bulb would be different in nature from the full spectrum light emitted by one of the noble plasma gases, as it is in the case of the Photon Stimulator, and certainly different from that emitted by an incandescent bulb.
	www.explorepub.com /articles/light_therapy.html (4777 words)

	Absorption spectroscopy Summary
		It is based on the absorption of quanta of light by a chemical substance, due to the promotion of electrons from one atomic orbital or molecular orbital to another in that substance.
		While the relative intensity of the several absorption lines does not vary, at a given wavelength the measured absorbance has been shown to be proportional to the molar concentration of the absorbing species and the thickness of the sample the light passes through.
		The absorption spectrum is measured using a spectrophotometer, which disperses the transmitted light using a diffraction grating and subtracts from the known incident spectrum to determine opacity at each wavelength in the measured range.
	www.bookrags.com /Absorption_spectroscopy (1344 words)

	Light Absorption & Scattering in Water Samples
		Light transfer through a water sample is affected in complex ways by water molecules, material dissolved in the water, and scattering by suspended particles.
		Light is an ensemble of photons that are absorbed and scattered by water, suspended particles, and dissolved matter as they travel through a sample.
		The absorption coefficient, a(λ), is a measure of the conversion of radiant energy to heat and chemical energy.
	www.d-a-instruments.com /light_absorption.html (1051 words)

	TPDSci Absorption Optoacoustic method
		In these methods, a sample is illuminated by a short pulse of light or by a light beam with modulated irradiance.
		Absorption of light in a zone of the sample illuminated by the beam causes a momentary temperature, and hence a pressure rise in that zone.
		Applications of optoacoustic methods range from measurements of the absorption of light by water (for example, Tam and Patel 1979), through measurements of the absorption of light by aerosols (for example, Arnott et al.
	www.tpdsci.com /Tpc/AbsOptAco.php (214 words)

	Conceptual Approach to Light Limitation
		The amount of light required for growth and reproduction (flowering) is the cumulative light received during the growing period of the plant's life history, typically spring and summer months for temperate seagrasses.
		Light attenuation by the water column is the major variable related to seagrass decline.
		Light absorption in water is the sum of contributions due to water itself, colored dissolved organic matter (CDOM), phytoplankton pigments, and non-algal particulate matter which consists of mineral and detrital particles, heterotrophic plankton, and the non-pigmented portion of algalcells.
	www.unc.edu /ims/paerllab/research/seagrass/concept.html (861 words)

	Olympus Microscopy Resource Center: Light and Color - Light Filters
		The absorption or transmission profile of filters, a critical element in defining filter action, is usually presented in the form of a wavelength plot (in nanometers; see Figures 1-4) versus the optical density, absorption, or transmission characteristics of the filter.
		Light that is incident on the multi-layer dielectric surface is either transmitted through the filter with constructive reinforcement, or reflected and reduced in magnitude by destructive interference (see Figure 6).
		Absorption neutral density filters are constructed from an emulsion of rare earth elements impregnated throughout the glass, and can be used in any orientation with respect to the illumination source.
	www.olympusmicro.com /primer/lightandcolor/filtersintro.html (6497 words)

	Spectroscopy (Site not responding. Last check: )
		Spectroscopy is the use of the absorption, emission, or scattering of electromagnetic radiation by atoms or molecules (or atomic or molecular ions) to qualitatively or quantitatively study the atoms or molecules, or to study physical processes.
		Redirection of light due to its interaction with matter is called scattering, and may or may not occur with transfer of energy, i.e., the scattered radiation has a slightly different or the same wavelength.
		Light that is scattered due to vibrations in molecules or optical phonons in solids is called Raman scattering.
	elchem.kaist.ac.kr /vt/chem-ed/spec/spectros.htm (470 words)

	Photon Absorption: Visible and X-rays
		X-ray absorption does depend on the energy of the x-rays and decreases with increasing x-ray energy, E. Absorption decreases nearly proportional to the cube of the energy (i.e.
		Light incident on a light absorbing material that is represented by a stack of equivalent thickness, t, layers.
		One notes from the table, that the mass absorption coefficient tends to increase with increase in atomic number (Z) and that the absorption coeficient is greater (in some cases a factor of ten greater) for the longer wavelength (lower energy) photons.
	acept.la.asu.edu /PiN/rdg/visnxray/visnxray.shtml (1715 words)

	Limnology and Oceanography Abstracts (Site not responding. Last check: )
		The specific light absorption by autotrophs was less variable over the three spectral bands considered than those of microheterotrophs and inorganic particles, which dropped sharply with increasing wavelength.
		Inorganic particles contributed, on the average, 48 and 74% of the total particulate absorption for the PAR waveband and at 400 nm, respectively, with their contribution to light absorption at 675 nm being negligible.
		Autotrophs dominated light absorption at 675 nm (on average 45.8% of total particulate absorption), whereas mixo- and heterotrophic ciliates and bacteria together contributed, on average, 22.5% of the total light absorption at this wavelength.
	www.aslo.org /lo/toc/vol_43/issue_2/0236.html (237 words)

	Optoelectronic devices (Site not responding. Last check: )
		Light absorption and emission in a semiconductor is known to be heavily dependent on the detailed band structure of the semiconductor.
		Absorption of a photon is obtained if an empty state in the conduction band is available for which the energy and momentum equals that of an electron in the valence band plus that of the incident photon.
		Figure 4.6.1(b) illustrates the absorption of a photon aided by the simultaneous absorption of a phonon, while Figure 4.6.1(c) depicts the absorption of a photon, which results in the emission of a phonon.
	ece-www.colorado.edu /~bart/book/book/chapter4/ch4_6.htm (2349 words)

	Olympus Microscopy Resource Center: Light and Color - Fluorescence - Overview of Excitation and Emission Fundamentals
		The absorption spectrum of a typical fluorochrome is illustrated in Figure 1(a) where the relative intensity of absorption is plotted against the measured wavelength.
		The yield of emitted light is referred to as the quantum yield, the ratio of the number of quanta ("packets" of energy) emitted compared to the number of quanta absorbed (usually the yield is between 0.1 and 0.9).
		Bleaching is irreversible decomposition of the fluorescent molecules because of light intensity in the presence of molecular oxygen.
	www.olympusmicro.com /primer/lightandcolor/fluoroexcitation.html (1833 words)

	Photoacoustic spectrometer for measuring light absorption by aerosol: Instrument description. - Arnott, Moosmller, ...
		Photoacoustic spectrometer for measuring light absorption by aerosol: Instrument description.
		The measured quantity is the sound pressure produced in an acoustic resonator caused by light absorption.
		The current lower detection limit for light absorption is 0.4 Mm -1 which corresponds to an elemental carbon mass density of 40 ng/m 3 assuming an efficiency for light absorption of 10 m 2 /g.
	citeseer.ist.psu.edu /arnott95photoacoustic.html (420 words)

	Atomic Absorption Spectrometry
		The principle used in atomic absorption spectroscopy was discovered in 1802 by Wollaston when he observed the "Fraunhofer lines" or absorption lines in the spectrum of the sun, yet this principle was only applied in 1955 by an Australian physicist, Alan Walsh.
		A light beam from a lamp whose cathode is made of the element in question is passed through the flame.
		Absorption at a selected wavelength is measured by the change in light intensity striking the detector and is directly related to the amount of the element in the sample.
	www.wesleylearning.ie /resources/science/chemistry/topics/instrumentation/aas/atomic_absorption_spectrometry.htm (590 words)

	Solar Energy Conversion by Dye-Sensitized Photovoltaic Cells (Site not responding. Last check: )
		The absorption of light by a monolayer of dye is weak because of the fact that the area occupied by one molecule is much larger than its optical cross section for light capture.
		to localize light in the mesoporous structure, augmenting the optical pathway significantly beyond the film thickness and enhancing the harvesting of photons in a spectral region where the optical cross section of the sensitizer is small.
		Even at 700 nm, where the absorption of light by the dye is weak, as shown in Figure 13, the IPCE value is still about 50%.
	pubs.acs.org /cgi-bin/sample.cgi/inocaj/2005/44/i20/html/ic0508371.html (6302 words)

	LED infrared skin rejuvination light anti-aging, wounds acne DPL Therapy as seen on TV informercials NASA Infra-Red
		Red or ultraviolet light was successfully used in the 19th century for the treatment of pockmarks and lupus vulgaris by Danish physician, N. Finsen, the father of contemporary phototherapy.
		For example, light having a wavelength of from 600 to 700, preferably from 630-680 nm, may be used for wound and ulcer healing.
		Light source is described by its spectrum, which shows the range of wavelengths of the emitted light.
	www.lighttherapyproducts.com /LEDMorestudies.html (2324 words)

	Why are rainbows & prism spectrums colored? (dispersive refraction)
		In the region of the absorption, the refractive index increases with the wavelength, instead of decreasing; this is difficult to observe since it occurs just where the light is most strongly absorbed.
		In a wellfaceted gemstone, a ray of light passing into the top of the stone is totally internally reflected and returned to the eye as the "brilliance." Since the geometry of the path corresponds to that in a prism, the reflected rays are also refracted, leading to flashes of color, the "fire" in a stone.
		Here the polarized light, on entering the crystal, is separated into ordinary and extraordinary rays moving at different velocities through the crystal; these rays are then recombined in the second polarizer to produce color by interference (see below).
	webexhibits.org /causesofcolor/13.html (658 words)

	Light Absorption in Thin Silicon.
		This is defined as the inverse distance in cm required for the intensity of incident light to fall to 1/e of its initial value.
		Because Si is an indirect-bandgap semiconductor, the absorption edge is not sharp, and for some of the thin-layer growth methods, useful light passes through the silicon without being absorbed.
		While 100% of the light is used in 300-mm wafers, this falls off to 90% in 50-mm thin layers and 70% in 10-mm thin layers.
	www.siliconsultant.com /SIlightab.htm (249 words)

	UV-Visible Spectroscopy (Site not responding. Last check: )
		In this respect the human eye is functioning as a spectrometer analyzing the light reflected from the surface of a solid or passing through a liquid.
		When sample molecules are exposed to light having an energy that matches a possible electronic transition within the molecule, some of the light energy will be absorbed as the electron is promoted to a higher energy orbital.
		The corrected absorption value is called "molar absorptivity", and is particularly useful when comparing the spectra of different compounds and determining the relative strength of light absorbing functions (chromophores).
	www.cem.msu.edu /~reusch/VirtualText/Spectrpy/UV-Vis/spectrum.htm (2049 words)

	Characterization of Methods for Measuring Aerosol Light Absorption (Site not responding. Last check: )
		The extinction cell measures the decrease in light transmitted through an air sample over a 6.6 meter path length, while the CRD instruments measure the decay of a short pulse of laser light as it bounces between two highly reflective mirrors over an effective path length of several tens of kilometers.
		The calibrations of these reference instruments are tied to the light scattering by carbon dioxide and air, and to measurements of temperature and pressure, all of which are well understood.
		The rate of this decrease, adjusted for sample flowrate and filtration area, is used to derive the aerosol light absorption.
	www.chemicalhouse.com:8080 /nl_new/jsp/viewnewsitem.jsp?id=466&newsitemid=755&type=technical&categoryname=Aerosol&sCategoryId=6 (652 words)

	C&A Template
		The absorption of red wavelengths is attributed to high vibrational transitions that have been shifted to lower energy levels by hydrogen bonding.
		The absorption of light in ice is similar to that of liquid water.
		While other factors such as light scattering and absorption by particles as well as reflections by water’s surface may change the observed color of water, pure water is a pale blue.
	www.sewanee.edu /Chem/Chem%26Art/Detail_Pages/ColorProjects_2004/Schildknecht/Schildknecht.htm (769 words)

	Reference.com/Encyclopedia/Transparency (optics)
		Though transparency usually refers to visible light in common usage, it may correctly be used to refer to any type of radiation.
		Where the degree of transparency varies according to the wavelength of the light, the image seen through the material is tinted.
		Opacity is based either on absorption or on reflection of the light falling onto the material.
	www.reference.com /browse/wiki/Transparency_%28optics%29 (363 words)

	NationMaster - Encyclopedia: CMYK (Site not responding. Last check: )
		The colors that are seen are from the part of light that is not absorbed.
		However the color a person sees on a computer screen is often slightly different from the color of the same object on a printout since CMYK and the RGB color model used in computer monitors have different gamuts.
		RGB color is made by the emission of light (additive color) whereas CMYK works by the absorption of it (subtractive color).
	www.nationmaster.com /encyclopedia/CMYK (593 words)

	TAPPI Website - Development of Light Absorption in Different Bleaching Stages Applied to Oxygen Delignified Softwood ...
		A method for determining light absorption of dissolved substance in terms which match the determination of light absorption in pulp has been tested on spent liquors from different bleaching stages applied to oxygen delignified softwood pulps.
		Light absorption of pulp before and after chlorination at two different chlorine charges and alkaline extraction, chlorine dioxide treatment and a reinforced alkaline extraction, ozone treatment as well as peroxide treatments was compared with that which was determined for the corresponding spent liquor.
		The net result of the treatments was that chlorination increased the total light absorption (of treated pulp and spent liquor) while chlorine dioxide, ozone and hydrogen peroxide decreased it.
	www.tappi.org /s_tappi/doc_bookstore.asp?CID=5394&DID=521531 (244 words)

	Photoacoustic and filter-based ambient aerosol light absorption measurements: Instrument comparisons and the role of ...
		Ambient measurements are reported of aerosol light absorption from photoacoustic and filter-based instruments (aethalometer and a particle soot absorption photometer (PSAP)) to provide insight on the measurement science.
		PSAP measurements of aerosol light absorption correlated very well with photoacoustic measurements, but the slope of the correlation indicated the PSAP values were larger by a factor of 1.61.
		This apparent decrease in light absorption with RH may be due to the contribution of mass transfer to the photoacoustic signal.
	www.agu.org /pubs/crossref/2003/2002JD002165.shtml (448 words)

	Process for making silicone intraocular lens with blue light absorption properties invention
		The blue light absorbing IOLs produced in accordance with the present invention protect an eye's retina from potentially damaging blue light and thereby possibly providing protection from macular degeneration.
		[0009] Blue light blocking silicone IOLs of the present invention are produced by exposing a semi-finished silicone IOL to an ethyleneically unsaturated yellow dye-containing solution and allowing the same to undergo a hydrosilation reaction.
		By absorbing blue light, the IOL serves to block blue light from reaching and potentially damaging the retina of an eye implanted with the IOL.
	www.freshpatents.com /Process-for-making-silicone-intraocular-lens-with-blue-light-absorption-properties-dt20060126ptan20060020340.php (1681 words)

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