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Topic: Light spectrum

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	Electromagnetic spectrum - Wikipedia, the free encyclopedia
		The electromagnetic spectrum, shown in the table, extends from frequencies used in the electric power grid (at the long-wavelength end) to gamma radiation (at the short-wavelength end), covering wavelengths from thousands of kilometres down to fractions of the size of an atom.
		If the spectrum is composed of background light, parts of which the object transmits and parts of which it absorbs, an absorption spectrum occurs.
		Visible light (and near-infrared light) is typically absorbed and emitted by electrons in molecules and atoms that move from one energy level to another.
	en.wikipedia.org /wiki/Electromagnetic_spectrum (1443 words)

	Reading on Color & Light, Part I
		The electromagnetic spectrum, which encompasses the visible region of light, extends from gamma rays with wave lengths of one hundredth of a nanometer to radio waves with wave lengths of one meter or greater.
		Orange light with a wavelength of 620 nanometers is composed of photons with energy of 2 eV.
		The region of visible light in wavelengths shown as a linear arrangement (a) and as a circle (b) as conceived by Sir Isaac Newton.
	acept.la.asu.edu /PiN/rdg/color/color.shtml (1625 words)

	Reading on Color and Light, Part II: Sources of Light
		The receptors of the eye respond to light in the visible spectrum and, as shown in Figure 1, the sun's spectrum encompasses the visible spectrum.
		Light from the sun is absorbed by the earth's atmosphere in the ultraviolet (UV) and infrared (IR) but some reaches the earth.
		Consequently, fluorescent tubes have an energy spectrum with a broad spectrum, similar to the tungsten lamp, and a series of sharp intense peaks in the red, blue, and green.
	acept.la.asu.edu /PiN/rdg/color/source.shtml (495 words)

	The Electromagnetic Spectrum (Site not responding. Last check: 2007-10-21)
		The electromagnetic spectrum is the distribution of electromagnetic radiation according to energy (or equivalently, by virtue of the relations in the previous section, according to frequency or wavelength).
		The visible part of the spectrum may be further subdivided according to color, with red at the long wavelength end and violet at the short wavelength end, as illustrated (schematically) in the following figure.
		In modern usage, indigo is not usually distinguished as a separate color in the visible spectrum; thus Roy no longer has any vowels in his last name.
	csep10.phys.utk.edu /astr162/lect/light/spectrum.html (205 words)

	Exploratorium: Science Snacks: Spectra
		Some other suggested light sources are a candle flame, the flame from a Bunsen burner, a flashlight, a camping lantern, yellow streetlights (sodium produces the color), blue streetlights (mercury vapor produces the color), neon signs, and slide projector lamps.
		The diffraction grating sorts light by frequency, with violet light (the highest frequency of visible light) at one end of the spectrum and red light (the lowest frequency of visible light) at the other.
		Each line in the spectrum of such a gas corresponds to one frequency of light emission, and is produced by an electron changing energy levels in the atom.
	www.exploratorium.edu /snacks/spectra.html (911 words)

	Howstuffworks "How Light Works"
		Light waves are a little more complicated, and they do not need a medium to travel through.
		A light wave consists of energy in the form of electric and magnetic fields.
		Light is one small part of the spectrum.
	science.howstuffworks.com /light2.htm (372 words)

	Importance of Light
		Full-spectrum light may be needed for the maintenance of health in ways still unknown, add, finally, light is important for the psychological well being of animals.
		Many bird owners place their pet's cage near a window or other light source, but that may not be enough to cure the problem, since glass can act as a filter, reflecting instead of transmitting certain portions of the spectrum.
		Once incandescent manufacturers figured out that people were being told to look for 'full spectrum' lighting, they started to market their wide spectrum (producing some, but not all of the visible wavelengths and no ultraviolet wavelengths) lights with 'full spectrum' in the ads and on packaging.
	www.prettybirds.net /Light.htm (1944 words)

	KryssTal : The Electromagnetic Spectrum
		Newton had showed that white light can be split into the spectrum by passing it through a triangular piece of glass called a prism.
		Light is the most familiar electromagnetic radiation because the Earth's atmosphere is transparent to it.
		Light (and a little of the Infra Red and Ultra Violet on either side of it) can pass through the atmosphere.
	www.krysstal.com /spectrum.html (1870 words)

	Electromagnetic Spectrum
		The narrow visible part of the electromagnetic spectrum corresponds to the wavelengths near the maximum of the Sun's radiation curve.
		White light may be separated into its spectral colors by dispersion in a prism.
		In interactions with matter, gamma rays are ionizing radiation and produce physiological effects which are not observed with any exposure of non-ionizing radiation, such as the risk of mutations or cancer in tissue.
	hyperphysics.phy-astr.gsu.edu /hbase/ems3.html (537 words)

	IAEEL NEWSLETTER 2/92 (Site not responding. Last check: 2007-10-21)
		Light meters and photometric devices are generally calibrated to the cone spectral sensitivity known as the photopic response.
		Several other initially puzzling findings of the effects of light spectrum on visual tasks and visual clarity that have been reported over the past 20 years can be simply understood by consideration of spectral effects on pupil size and the concept of the pupil lumen.
		To determine the value of the pupil luminance for a given lighting condition requires knowing both the scotopic and photopic values, and their ratio S/P. In many cases this ratio is independent of the intensity level of the illumination.
	www.iaeel.org /IAEEL/NEWSL/1992/tva1992/HumFa_2_92.html (1195 words)

	The Electromagnetic Spectrum
		To start with you should know what a spectrum is: when white light is shone through a prism it is separated out into all the colours of the rainbow; this is the visible spectrum.
		The light with the longest wavelength (red) is absorbed by the green stuff (chlorophyll) in the leaves.
		Well it is easy to explain some of the properties of light by pretending that it is made of tiny particles called photons and it is easy to explain other properties of light by pretending that it is some kind of wave.
	www.purchon.com /physics/electromagnetic.htm (1217 words)

	Blue Sky - Why is the Sky Blue?
		Light is a wave of vibrating electric and magnetic fields.
		Light from the sun or a light bulb may look white, but it is actually a combination of many colors.
		Light from the sun or a light bulb looks white, but it is really a mixture of many colors.
	www.sciencemadesimple.com /sky_blue.html (2850 words)

	Optimizing Light Spectrum for Long-Duration Space Flight
		From this data, it may be possible to optimize the light spectrum both as a phase-shifting or entrainment countermeasure for specific circadian disturbances before or during space flight and for healthier illumination of spacecraft interiors in general.
		The results can be used to improve light treatment as a countermeasure for circadian and sleep-wake disruption in NASA space flight missions, identify the best spectral transmission for space suit visors and the windows used in space vehicles and habitats, and engineer the ideal spectral distribution for illumination of general living quarters during space exploration.
		The lighting industry has taken notice of the biological impact different types of light is capable of having, and has already begun to invest in furthering our understanding of lights role for human health.
	www.nsbri.org /Research/Projects/viewsummary.epl?pid=44 (1330 words)

	Full-Spectrum Light
		But when the ends of the light tubes are shielded with lead and traces of UV are added to the light, plants and animals under them grow and function normally.
		If those wavelengths are missing in the artificial light source a person is exposed to, then the nutritional or other hoped-for benefits of the substance will not be utilized." UV functions as a nutrient and as a cofactor (substance required for a bodily process to occur) in utilization of other nutrients.
		So the full spectrum lights corrected the children's deficiency of vitamin D3 (which is not the same as the toxic form of vitamin D that is added to milk), now considered a pro-hormone.
	www.heall.com /healingnews/nov/full_spectrum_lighting.html (5777 words)

	Electromagnetic Spectrum (Site not responding. Last check: 2007-10-21)
		Visible light is made up of electromagnetic waves, vibrations of electric and magnetic fields that propagate through space.
		The wavelength of such light is but 700 nanometers long,which means that one wave spans only 7/10 000 000, or 7 ten millionths of a meter.
		Measuring a single wavelength of this light against the length of a meter is like comparing a thumbtack's diameter to the distance across the United States.
	archive.ncsa.uiuc.edu /Cyberia/Bima/spectrum.html (411 words)

	Search Results for spectrum - Encyclopædia Britannica
		It was seen, in the preceding section, that white light can be dispersed into a spectrum by refraction, by diffraction, or by interference.
		As the electrons move closer to or farther from the nucleus of an atom (or of an ion), energy in the form of light (or...
		Portion of the electromagnetic spectrum that extends from the...
	www.britannica.com /search?query=spectrum (547 words)

	Can Plants "See" Light? (Site not responding. Last check: 2007-10-21)
		The light that cannot be seen with the unaided eye includes far-red and ultraviolet rays, both of which can affect plant growth.
		Light is made up of many units of energy called photons and travels in wavelengths at the speed of light (186,000 miles per second).
		The light is absorbed by the green pigment chlorophyll, which is located in the leaves of the plant.
	www.florence.ars.usda.gov /kidsonly/middle/mulch3.html (322 words)

	Electromagnetic Spectrum - Introduction
		The electromagnetic (EM) spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group.
		Radiation is energy that travels and spreads out as it goes-- visible light that comes from a lamp in your house or radio waves that come from a radio station are two types of electromagnetic radiation.
		Electromagnetic radiation from space is unable to reach the surface of the Earth except at a very few wavelengths, such as the visible spectrum, radio frequencies, and some ultraviolet wavelengths.
	imagine.gsfc.nasa.gov /docs/science/know_l1/emspectrum.html (1301 words)

	Visible Light Waves
		When white light shines through a prism or through water vapor like this rainbow, the white light is broken apart into the colors of the visible light spectrum.
		Light bulbs are another source of visible light waves.
		However, since visible light is the part of the electromagnetic spectrum that our eyes can see, our whole world is oriented around it.
	imagers.gsfc.nasa.gov /ems/visible.html (691 words)

	Wired News: Beaming Video at Speed of Light
		It was this light that brought the singer's performance to the 100 or so in the audience this week in what is believed to be the first live broadcast of high-quality television images over visible light spectrum.
		But by using light-emitting diodes as the light source, instead of lasers, Power Beat says the system, dubbed Megamantis, is easier to align.
		Light concentrators at the receiving end also mean that less accurate alignment is required than what's required with lasers.
	www.wired.com /news/infostructure/0,1377,57860,00.html (876 words)

	Atomic Absorption and Emission Spectra
		When the corresponding light is passed through a prism or spectrograph it is separated spatially according to wavelength, as illustrated in the following image.
		An absorption spectrum occurs when light passes through a cold, dilute gas and atoms in the gas absorb at characteristic frequencies; since the re-emitted light is unlikely to be emitted in the same direction as the absorbed photon, this gives rise to dark lines (absence of light) in the spectrum.
		The spectrum of hydrogen is particularly important in astronomy because most of the Universe is made of hydrogen.
	csep10.phys.utk.edu /astr162/lect/light/absorption.html (408 words)

	Cowley Lecture 12 - Light and the Electromagnetic Spectrum: The Astronomer's Tools (Site not responding. Last check: 2007-10-21)
		Herschel found that the temperature increased toward the red end of the spectrum and continued to increase as he moved the thermometer into the dark portion beyond the red end of the visible light spectrum.
		In particular, light rays near the axis of the mirror may not come to the same focus as rays near the edge.
		Fraunhofer in 1817 labeled the most prominent absorption lines in the spectrum of the sun; it's for this reason that the two intense yellow lines in the spectrum of sodium are called the Fraunhofer D lines.
	www.astro.lsa.umich.edu /users/cowley/lecture12 (5777 words)

	Halogen light Spectrum, the Fluorescent Spectrum (Site not responding. Last check: 2007-10-21)
		This is due to the unique properties that these lights tend to have higher intensities on one particular type of light, or around some particular wavelength, and little intensity ate the rest of the light spectrum.
		Thus, from the spectrum, we are able to see that the fluorescent light has more blue light, or that the type of light with the highest intensity, and hence highest amplitude, is the blue light.
		This is why Fluorescent lights are mixed with other types of lights to produce a light that is closer to sunlight.
	www.mtholyoke.edu /~mpeterso/classes/phys301/projects2001/awgachor/awgachor.htm (231 words)

	Spectrum Applet (Site not responding. Last check: 2007-10-21)
		This applet demonstrates how a spectrum is related to the perceived color.
		Each point on the spectrum represents the relative value of the power distribution at the particular wavelength.
		As the spectrum is modified, the corrensponding CIE X,Y,Z primaries are updated automatically.
	www.cs.rit.edu /~ncs/color/a_spectr.html (125 words)

	The Science of Light
		Seeing colors and shapes is second nature to us, yet light is a perplexing phenomenon when we study it more closely.
		Light acts like particles—little light bullets—that stream from the source.
		Light behaves according to special rules; for example, it usually travels in a straight line and it bounces off mirrors at the same angle it hits them.
	www.learner.org /teacherslab/science/light (266 words)

	The Electromagnetic Spectrum - Index page (Site not responding. Last check: 2007-10-21)
		The electromagnetic spectrum is something that is more familiar than one might think.
		The light that our eyes can see is actually part of the electromagnetic spectrum.
		This visible part of the electromagnetic spectrum consists of the colors that we see in a rainbow - from reds and oranges, through blues and purples.
	imagers.gsfc.nasa.gov /ems/ems.html (65 words)

	The EM Spectrum (Site not responding. Last check: 2007-10-21)
		Optical light is only a small part of the much more expansive electromagnetic spectrum that includes everything from so-called gamma rays at the shortest wavelengths to radio waves at the longest wavelengths.
		The violet and red "ends" of the optical spectrum are not really "ends" at all, but rather simply the limits to the portion of the EM spectrum to which our eyes are sensitive.
		Likewise, beyond the violet of the optical spectrum lies a broad region known as the ultraviolet, which blends into the X-ray region, followed by the the shortest wavelength radiation known, the gamma rays.
	fuse.pha.jhu.edu /~wpb/spectroscopy/em_spec.html (624 words)

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