query: materials that clearly transmit visible light are said to be

pos: Transparency and translucency by some combination of reflection, absorption and transmission. Some materials, such as plate glass and clean water, transmit much of the light that falls on them and reflect little of it; such materials are called optically transparent. Many liquids and aqueous solutions are highly transparent. Absence of structural defects (voids, cracks, etc.) and molecular structure of most liquids are mostly responsible for excellent optical transmission. Materials which do not transmit light are called opaque. Many such substances have a chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of white light

neg: Glass in widespread use largely due to the production of glass compositions that are transparent to visible light. In contrast, polycrystalline materials do not generally transmit visible light. The individual crystallites may be transparent, but their facets (grain boundaries) reflect or scatter light resulting in diffuse reflection. Glass does not contain the internal subdivisions associated with grain boundaries in polycrystals and hence does not scatter light in the same manner as a polycrystalline material. The surface of a glass is often smooth since during glass formation the molecules of the supercooled liquid are not forced to dispose in rigid crystal geometries

neg: Solid response several times larger than the traditional piezoelectric material quartz (crystalline SiO). The deformation (~0.1%) lends itself to useful technical applications such as high-voltage sources, loudspeakers, lasers, as well as chemical, biological, and acousto-optic sensors and/or transducers. Materials can transmit (e.g. glass) or reflect (e.g. metals) visible light. Many materials will transmit some wavelengths while blocking others. For example, window glass is transparent to visible light, but much less so to most of the frequencies of ultraviolet light that cause sunburn. This property is used for frequency-selective optical filters, which can alter the color of incident light. For some purposes,

neg: Ceramic the military sector for high-strength, robust materials which have the capability to transmit light (electromagnetic waves) in the visible (0.4 – 0.7 micrometers) and mid-infrared (1 – 5 micrometers) regions of the spectrum. These materials are needed for applications requiring transparent armor, including next-generation high-speed missiles and pods, as well as protection against improvised explosive devices (IED). In the 1960s, scientists at General Electric (GE) discovered that under the right manufacturing conditions, some ceramics, especially aluminium oxide (alumina), could be made translucent. These translucent materials were transparent enough to be used for containing the electrical plasma generated in high-pressure sodium

neg: Optical fiber cable as within cars. Each connection made adds about 0.6 dB of average loss, and each joint (splice) adds about 0.1 dB. Depending on the transmitter power and the sensitivity of the receiver, if the total loss is too large the link will not function reliably. Invisible infrared light is used in commercial glass fiber communications because it has lower attenuation in such materials than visible light. However, the glass fibers will transmit visible light somewhat, which is convenient for simple testing of the fibers without requiring expensive equipment. Splices can be inspected visually, and adjusted for minimal light leakage at

neg: Transparency and translucency When light strikes an object, it usually has not just a single frequency (or wavelength) but many. Objects have a tendency to selectively absorb, reflect or transmit light of certain frequencies. That is, one object might reflect green light while absorbing all other frequencies of visible light. Another object might selectively transmit blue light while absorbing all other frequencies of visible light. The manner in which visible light interacts with an object is dependent upon the frequency of the light, the nature of the atoms in the object, and often the nature of the electrons in the atoms of the

neg: Visible light communication but cannot perceive the instantaneous color that varies rapidly in time. In other words, CSK transmission maintains a constant time-averaged luminous flux, even as its symbol sequence varies rapidly in chromaticity. Visible light communication Visible light communication (VLC) is a data communications variant which uses visible light between 400 and 800 THz (780–375 nm). VLC is a subset of optical wireless communications technologies. The technology uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kbit/s, or LEDs for up to 500 Mbit/s over short distances. Systems such as RONJA can transmit at full Ethernet speed

neg: Photographic paper blue to green light, the contrast of the print can be approximately continuously varied between these extremes, creating all contrast grades from 00 to 5. Filters in the enlarger's light path are a common method of achieving this control. Magenta filters absorb green and transmit blue and red, while yellow filters absorb blue and transmit green and red. The contrast of photographic papers can also be controlled during processing or by the use of bleaches or toners. Panchromatic black-and-white photographic printing papers are sensitive to all wavelengths of visible light. They were designed for the printing of full-tone black-and-white images

neg: 3D television LCD business, said that the demand for 3D TV would skyrocket in the next couple of years, fueled by televised sports (but this did not happen). One might be able to obtain information directly onto their television due to new technologies like the Visible Light Communication that allows for this to happen because the LED lights transmit information by flickering at high frequencies. The basic requirement is to display offset images that are filtered separately to the left and right eye. Two strategies have been used to accomplish this: have the viewer wear eyeglasses to filter the separately offset images

neg: Li-Fi Li-Fi Li-Fi (; short for "light fidelity") is a technology for wireless communication between devices using light to transmit data and position. In its present state only LED lamps can be used for the transmission of visible light. The term was first introduced by Harald Haas during a 2011 TEDGlobal talk in Edinburgh. In technical terms, Li-Fi is a visible light communications system that is capable of transmitting data at high speeds over the visible light spectrum, ultraviolet and infrared radiation. In terms of its end use the technology is similar to Wi-Fi. The key technical difference is that Wi-Fi

neg: Visible light communication Visible light communication Visible light communication (VLC) is a data communications variant which uses visible light between 400 and 800 THz (780–375 nm). VLC is a subset of optical wireless communications technologies. The technology uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kbit/s, or LEDs for up to 500 Mbit/s over short distances. Systems such as RONJA can transmit at full Ethernet speed (10 Mbit/s) over distances of . Specially designed electronic devices generally containing a photodiode receive signals from light sources, although in some cases a cell phone camera or a digital camera

neg: Solar gain Solar gain Solar gain (also known as solar heat gain or passive solar gain) refers to the increase in thermal energy of a space, object or structure as it absorbs incident solar radiation. The amount of solar gain a space experiences is a function of the total incident solar irradiance and of the ability of any intervening material to transmit or resist the radiation. Objects struck by sunlight absorb its visible and short-wave infrared components, increase in temperature, and then re-radiate that heat at longer infrared wavelengths. Though transparent building materials such as glass allow visible light to pass through

neg: Transparent ceramics depending on the material system, and there does not appear to be any general consensus regarding strengthening mechanisms, even within a given system. In the SiC/AlO system, for example, it is widely known and accepted that the addition of SiC particles to the AlO matrix results in a change of failure mechanism from intergranular (between grains) to intragranular (within grains) fracture. The explanations for improved strength include: There is an increasing need in the military sector for high-strength, robust materials which have the capability to transmit light around the visible (0.4–0.7 micrometers) and mid-infrared (1–5 micrometers) regions of the spectrum.

neg: Extreme ultraviolet Imaging Telescope and specially thinned to admit the EUV photons. Because the detector is about equally sensitive to EUV and visible photons, and the Sun is about one billion (10) times brighter in visible light than in EUV, special thin foil filters are used to block the visible light while admitting the EUV. The filters are made of extremely thin aluminum foil, about 200 nm (0.2 micrometre) thick, and transmit about half of the incident EUV light while absorbing essentially all of the incident visible light. EIT was a difficult sell to the scientific funding agencies, as it was not clear in

neg: History of radar transmit through different types of materials and also would reflect off metal surfaces in his lab as well as conductors and dielectrics. The nature of these waves being similar to visible light in their ability to be reflected, refracted, and polarized would be shown by Hertz and subsequent experiments by other physicists. Radio pioneer Guglielmo Marconi noticed radio waves were being reflected back to the transmitter by objects in radio beacon experiments he conducted on March 3, 1899 on Salisbury Plain. In 1916 he and a British engineer called Charles Samuel Franklin used short-waves in their experiments, critical to the

neg: Li-Fi $6 billion per year by 2018. Visible light communications (VLC) works by switching the current to the LEDs off and on at a very high rate, too quick to be noticed by the human eye. Although Li-Fi LEDs would have to be kept on to transmit data, they could be dimmed to below human visibility while still emitting enough light to carry data. The light waves cannot penetrate walls which makes a much shorter range, though more secure from hacking, relative to Wi-Fi. Direct line of sight is not necessary for Li-Fi to transmit a signal; light reflected off the

neg: Transparent ceramics incident light wave), optical transparency in polycrystalline materials is limited by the amount of light that is scattered by their microstructural features. The amount of light scattering therefore depends on the wavelength of the incident radiation, or light. For example, since visible light has a wavelength scale on the order of hundreds of nanometers, scattering centers will have dimensions on a similar spatial scale. Most ceramic materials, such as alumina and its compounds, are formed from fine powders, yielding a fine grained polycrystalline microstructure that is filled with scattering centers comparable to the wavelength of visible light. Thus, they are

neg: Dichroism Dichroism In optics, a dichroic material is either one which causes visible light to be split up into distinct beams of different wavelengths (colours) (not to be confused with dispersion), "or" one in which light rays having different polarizations are absorbed by different amounts. The original meaning of "dichroic", from the Greek "dikhroos", two-coloured, refers to any optical device which can split a beam of light into two beams with differing wavelengths. Such devices include mirrors and filters, usually treated with optical coatings, which are designed to reflect light over a certain range of wavelengths, and transmit light which is

neg: Dispersion (optics) as "angular dispersion". For visible light, refraction indices "n" of most transparent materials (e.g., air, glasses) decrease with increasing wavelength "λ": or alternatively: In this case, the medium is said to have "normal dispersion". Whereas, if the index increases with increasing wavelength (which is typically the case in the ultraviolet), the medium is said to have "anomalous dispersion". At the interface of such a material with air or vacuum (index of ~1), Snell's law predicts that light incident at an angle "θ" to the normal will be refracted at an angle arcsin(). Thus, blue light, with a higher refractive index,

neg: Voyeurism they would have qualified as "spy cameras", and digital cameras of twenty megapixels or more are now being embedded in some mobile camera phones. The vast majority of mobile phones in use are camera phones. Certain image capturing devices are capable of producing images through materials that are opaque to visible light, including clothing. These devices form images by using electromagnetic radiation outside the visible range. Infrared and terahertz-wave cameras are capable of creating images through clothing, though these images differ from what would be created with visible light. Candaulism is a sexual practice or fantasy in which a man

neg: Ceramic engineering World War II encouraged developments, which created a need for high-performance materials and helped speed the development of ceramic science and engineering. Throughout the 1960s and 1970s, new types of ceramics were developed in response to advances in atomic energy, electronics, communications, and space travel. The discovery of ceramic superconductors in 1986 has spurred intense research to develop superconducting ceramic parts for electronic devices, electric motors, and transportation equipment. There is an increasing need in the military sector for high-strength, robust materials which have the capability to transmit light around the visible (0.4–0.7 micrometers) and mid-infrared (1–5 micrometers) regions of

neg: Mars impact craters: a total of 43,000 craters with a diameter of or greater have been found. The largest confirmed of these is the Hellas impact basin, a light albedo feature clearly visible from Earth. Due to the smaller mass of Mars, the probability of an object colliding with the planet is about half that of Earth. Mars is located closer to the asteroid belt, so it has an increased chance of being struck by materials from that source. Mars is more likely to be struck by short-period comets, "i.e.", those that lie within the orbit of Jupiter. In spite of

neg: Nucleoid large compared to the dimensions of the cell, and the genomic DNA molecules must be compacted to fit. The nucleoid can be clearly visualized on an electron micrograph at high magnification, where, although its appearance may differ, it is clearly visible against the cytosol. Sometimes even strands of what is thought to be DNA are visible. By staining with the Feulgen stain, which specifically stains DNA, the nucleoid can also be seen under a light microscope. The DNA-intercalating stains DAPI and ethidium bromide are widely used for fluorescence microscopy of nucleoids.It have a irregular shape and found in prokaryotic cells.

neg: Infrared lamp different materials. Solid-state light emitting diodes can be produced to be efficient sources of near-monochromatic infrared energy. Such sources can be rapidly modulated for communication systems and control signals. A light emitting diode can be closely coupled to an optical fiber, allowing infrared signals to be sent up to scores of kilometres without amplification. Infrared heating uses infrared lamps, commonly called heat lamps to transmit infrared radiation to the body that is being heated. When bodies with a large surface area need to be heated, infrared lamps are often used in banks. Infrared heat lamps are commonly incandescent bulbs which

neg: Mirror is an important consideration. The transmissivity of metallic coatings are often determined by their thickness. For precision beam-splitters or output couplers, the thickness of the coating must be kept at very high tolerances to transmit the proper amount of light. For dielectric mirrors, the thickness of the coat must always be kept to high tolerances, but it is often more the number of individual coats that determine the transmissivity. For the substrate, the material used must also have good transmissivity to the chosen wavelengths. Glass is a suitable substrate for most visible-light applications, but other substrates such as zinc selenide

neg: Optical answer sheet read. In this way students' answers can be digitally recorded, or identity given. The first optical answer sheets were read by shining a light through the sheet and measuring how much of the light was blocked using phototubes on the opposite side. As some phototubes are mostly sensitive to the blue end of the visible spectrum, blue pens could not be used, as blue inks reflect and transmit blue light. Because of this, number two pencils had to be used to fill in the bubbles—graphite is a very opaque substance which absorbs or reflects most of the light which hits

neg: Wide-bandgap semiconductor Their higher energy density handling is particularly interesting in attempts to extend Moore's law, where conventional technologies appear to be reaching a density plateau. Wide bandgap materials have several characteristics that make them useful compared to lower bandgap materials. The higher energy gap gives devices the ability to operate at higher temperatures, and for some applications, allows devices to switch larger voltages. The wide bandgap also brings the electronic transition energy into the range of the energy of visible light, and hence light-emitting devices such as light-emitting diodes (LEDs) and semiconductor lasers can be made that emit in the visible

neg: Spectrophotometry emits IR light as thermal radiation, especially at wavelengths beyond about 5 μm. Another complication is that quite a few materials such as glass and plastic absorb infrared light, making it incompatible as an optical medium. Ideal optical materials are salts, which do not absorb strongly. Samples for IR spectrophotometry may be smeared between two discs of potassium bromide or ground with potassium bromide and pressed into a pellet. Where aqueous solutions are to be measured, insoluble silver chloride is used to construct the cell. Spectroradiometers, which operate almost like the visible region spectrophotometers, are designed to measure the spectral

neg: Ellipsometry about film thickness, the light reflecting off of the substrate must be nulled. Nulling is achieved by adjusting the analyzer and polarizer so that all reflected light off of the substrate is extinguished. Due to the difference in refractive indexes, this will allow the sample to become very bright and clearly visible. The light source consists of a monochromatic laser of the desired wavelength. A common wavelength that is used is 532 nm green laser light. Since only intensity of light measurements are needed, almost any type of camera can be implemented as the CCD, which is useful if building

neg: 2.5D larger with each step, as to give the effect of an object coming closer and closer towards the player. Even simple shading and size of an image could be considered pseudo-3D, as shading makes it look more realistic. If the light in a 2D game were 2D, it would only be visible on the outline, and because outlines are often dark, they would not be very clearly visible. However, any visible shading would indicate the usage of pseudo-3D lighting and that the image uses pseudo-3D graphics. Changing the size of an image can cause the image to appear to be

neg: Daylighting meters. Typically only a few percent of the light is transmitted (the percent transmittance is about half the percent of the surface that is fibers, and usually only ~5% fibers are used). Both glass and concrete conduct heat fairly well, when solid, so none of these walls insulate well. They are therefore often used outdoors, as a divider between two heated spaces (see images), or in very temperate climates. Greenhouse walls (and rooves) are made to transmit as much light and as little heat as possible. They use a variety of materials, and may be transparent or translucent. "See anidolic

neg: Machine Identification Code the TU Dresden analyzed the patterns of 106 printer models from 18 manufacturers and found four different encoding schemes. The Machine Identification Code can be made visible by printing or copying a page and subsequently scanning a small section with a high-resolution scanner. The yellow color channel can then be enhanced with an image processing program, to make any dots of the MIC clearly visible. Under good lighting conditions, a magnifying glass may be enough to see the pattern. Under UV-light the yellow dots are clearly recognizable. Using this steganographic process, high-quality copies of an original (e.g. a bank note)

neg: History of climate change science visible light waves efficiently to the earth's surface. The earth then absorbed visible light and emitted infrared radiation in response, but the atmosphere did not transmit infrared efficiently, which therefore increased surface temperatures. He also suspected that human activities could influence climate, although he focused primarily on land use changes. In an 1827 paper Fourier stated, ""The establishment and progress of human societies, the action of natural forces, can notably change, and in vast regions, the state of the surface, the distribution of water and the great movements of the air. Such effects are able to make to vary, in

neg: Dental curing light can be dispensed directly into the site. This new malleable resin material can only be fully cured/hardened with a dental curing light. This presents new advantages for dentists: the time constraint is now lifted and the dentist can now assure that the material is properly placed. Dental curing light A dental curing light is a piece of dental equipment that is used for polymerization of light cure resin based composites. It can be used on several different dental materials that are curable by light. The light used falls under the visible blue light spectrum. This light is delivered over a

neg: Fluorescent lamp built in the same fashion as conventional fluorescent lamps but the glass tube is coated with a phosphor that converts the short-wave UV within the tube to long-wave UV rather than to visible light. They are used to provoke fluorescence (to provide dramatic effects using blacklight paint and to detect materials such as urine and certain dyes that would be invisible in visible light) as well as to attract insects to bug zappers. So-called "blacklite blue" lamps are also made from more expensive deep purple glass known as Wood's glass rather than clear glass. The deep purple glass filters out

neg: Dental curing light Dental curing light A dental curing light is a piece of dental equipment that is used for polymerization of light cure resin based composites. It can be used on several different dental materials that are curable by light. The light used falls under the visible blue light spectrum. This light is delivered over a range of wavelengths and varies for each type of device. There are four basic types of dental curing light sources: tungsten halogen, light-emitting diodes (LED), plasma arcs, and lasers. The two most common are halogen and LEDs. In the early 1960s, the first light curing resin

neg: Transparent conducting film indium tin oxide (ITO), fluorine doped tin oxide (FTO) or doped zinc oxide. Organic films are being developed using carbon nanotube networks and graphene, which can be fabricated to be highly transparent to infrared light, along with networks of polymers such as poly(3,4-ethylenedioxythiophene) and its derivatives. Transparent conducting films are typically used as electrodes when a situation calls for low resistance electrical contacts without blocking light (e.g. LEDs, photovoltaics). Transparent materials possess wide bandgaps whose energy value is greater than those of visible light. As such, photons with energies below the bandgap value are not absorbed by these materials and

neg: Bicycle lighting option powered from the main battery pack. Retro-reflective materials, in the form of fixed reflectors, reflective tape, and reflective clothing, are useful in making a cyclist visible to other road users. Reflective materials can be applied to bike, rider, or luggage; also, tires are available with reflective sidewalls. Reflectives are visible only when in the beam of a headlight, and even then only within a narrow locus. Importantly, they "do nothing to light up the road". Reflectors are "not" a substitute for lights, but are an important supplement to portable lighting. Reflectors and reflective tape provide additional visibility (especially when

neg: Computers, Freedom and Privacy Conference of conference bag included some with a subtle but visible flashing red light behind the dome. Not all of the wireless web cameras had flashing red lights, and some of the flashing red lights were dummy devices that did not transmit video. The bags that did transmit video also updated various video displays around the conference hall, visible to conference attendees. The twenty-first annual CFP Conference in 2011, "Computers, Freedom, and Privacy: The Future is Now", was held at the Georgetown Law Center in Washington, DC June 14–16. Among the questions and issues explored were: What is social media’s role

neg: Metamaterial cloaking and lenses have a long history of altering the diffracted visible light that surrounds all. However, the control exhibited by these ordinary materials is limited. Moreover, the one material which is common among these three types of directors of light is conventional glass. Hence, these familiar technologies are constrained by the fundamental, physical laws of optics. With metamaterials in general, and the cloaking technology in particular, it appears these barriers disintegrate with advancements in materials and technologies never before realized in the natural physical sciences. These unique materials became notable because electromagnetic radiation can be bent, reflected, or skewed in

neg: Last mile unguided nature makes them more susceptible to unwanted noise and signals. Spectral reuse can therefore be limited. Visible and infrared light waves are much shorter than radio frequency waves. Their use to transmit data is referred to as free-space optical communication. Being short, light waves can be focused or collimated with a small lens/antenna, and to a much higher degree than radio waves. Thus, a receiving device can recover a greater portion of the transmitted signal. Also, because of the high frequency, a high data transfer rate may be available. However, in practical last mile environments, obstructions and de-steering of

neg: Chromatophore selectively absorb parts of the visible light spectrum that makes up white light while permitting other wavelengths to reach the eye of the observer. Structural colours are produced by various combinations of diffraction, reflection or scattering of light from structures with a scale around a quarter of the wavelength of light. Many such structures interfere with some wavelengths (colours) of light and transmit others, simply because of their scale, so they often produce iridescence, creating different colours when seen from different directions. Whereas all chromatophores contain pigments or reflecting structures (except when there has been a mutation, as in albinism),

neg: Faraday effect to R-rotation (clockwise) when the direction of propagation is anti-parallel. Thus, if a ray of light is passed through a material and reflected back through it, the rotation doubles. Some materials, such as terbium gallium garnet (TGG) have extremely high Verdet constants (≈ for 632 nm light). By placing a rod of this material in a strong magnetic field, Faraday rotation angles of over 0.78 rad (45°) can be achieved. This allows the construction of Faraday rotators, which are the principal component of Faraday isolators, devices which transmit light in only one direction. The Faraday effect can, however, be observed

neg: Particle in a box inversely proportional to wavelength. The smaller the quantum dot, the larger the band gap and thus the shorter the wavelength absorbed. Different semiconducting materials are used to synthesize quantum dots of different sizes and therefore emit different wavelengths of light. Materials that normally emit light in the visible region are often used and their sizes are fine-tuned so that certain colors are emitted. Typical substances used to synthesize quantum dots are cadmium (Cd) and selenium (Se). For example, when the electrons of two nanometer CdSe quantum dots relax after excitation, blue light is emitted. Similarly, red light is emitted in

neg: Negative-index metamaterial above section a left-handed material (LHM) can be defined. It is a material which exhibits simultaneous negative values for permittivity, ε, and permeability, μ, in an overlapping frequency region. Since the values are derived from the effects of the composite medium system as a whole, these are defined as effective permittivity, ε, and effective permeability, μ. Real values are then derived to denote the value of negative index of refraction, and wave vectors. This means that in practice losses will occur for a given medium used to transmit electromagnetic radiation such as microwave, or infrared frequencies, or visible light –

neg: Portland Head Light of the construction of a lighthouse on Portland Head. Washington reminded them that the early government was poor, and said that the materials used to build the lighthouse should be taken from the fields and shores, which could be handled nicely when hauled by oxen on a drag. The original plans called for the tower to be 58 feet tall. When the masons completed this task they climbed to the top of the tower and realized that it would not be visible beyond the headlands to the south, so it was raised approximately 20 feet. The tower was built of

neg: Visual control control methods aim to increase the efficiency and effectiveness of a process by making the steps in that process more visible. The theory behind visual control is that if something is clearly visible or in plain sight, it is easy to remember and keep at the forefront of the mind. Another aspect of visual control is that everyone is given the same visual cues and so are likely to have the same vantage point. There are many different techniques that are used to apply visual control in the workplace. Some companies use visual control as an organizational tool for materials.

neg: Book of Optics accidental objects. Accidental light can only exist if there is a source of primary light. Both primary and secondary light travel in straight lines. Transparency is a characteristic of a body that can transmit light through them, such as air and water, although no body can completely transmit light or be entirely transparent. Opaque objects are those through which light cannot pass through directly, although there are degrees of opaqueness which determine how much light can actually pass through. Opaque objects are struck with light and can become luminous bodies themselves which radiate secondary light. Light can be refracted by

neg: Automotive lighting presence, position and direction of travel clearly visible from oblique angles. The lights are wired so as to illuminate whenever the vehicles' parking and taillamps are on, including when the headlamps are being used. Front amber side markers in the United States may be wired so as to flash in synchronous phase or opposite-phase with the turn signals; nevertheless, they are not required to flash at all. Side markers are permitted but not required on cars and light passenger vehicles outside the United States and Canada. If installed, they are required to be brighter and visible through a larger horizontal

neg: Infrared used is divided into seven bands based on availability of light sources transmitting/absorbing materials (fibers) and detectors: The C-band is the dominant band for long-distance telecommunication networks. The S and L bands are based on less well established technology, and are not as widely deployed. Infrared radiation is popularly known as "heat radiation", but light and electromagnetic waves of any frequency will heat surfaces that absorb them. Infrared light from the Sun accounts for 49% of the heating of Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths. Visible light or ultraviolet-emitting

neg: Expo 2010 pavilions Italcementi Group, an Italy-based cement maker, developed the transparent cement employed to build the pavilion. Although the Italian group has not fully disclosed what was put into the mixture to make the cement, they said it contains transparent thermoplastic resin and inorganic materials such as alumina which can become solid without the use of water. Each block was able to transmit 20% of the light passing through.，the cement blocks itself was produced in Taiwan by Romastone Hong Hao, director of the Bureau of World Expo Shanghai Coordination, said that since Milan won the bid to host World Expo 2015, Italy

neg: Whiteout (weather) Whiteout (weather) Whiteout is a weather condition in which visibility and contrast are severely reduced by snow or sand. The horizon disappears from view while the sky and landscape appear featureless, leaving no points of visual reference by which to navigate. Whiteout has been defined as: "A condition of diffuse light when no shadows are cast, due to a continuous white cloud layer appearing to merge with the white snow surface. No surface irregularities of the snow are visible, but a dark object may be clearly seen. There is no visible horizon." A whiteout may be due simply to extremely

neg: Building insulation Some radiant barriers are spectrally selective and will preferentially reduce the flow of infra-red radiation in comparison to other wavelengths. For instance low-emissivity (low-e) windows will transmit light and short-wave infra-red energy into a building but reflect the long-wave infra-red radiation generated by interior furnishings. Similarly, special heat-reflective paints are able to reflect more heat than visible light, or vice versa. Thermal emissivity values probably best reflect the effectiveness of radiant barriers. Some manufacturers quote an 'equivalent' R-value for these products but these figures can be difficult to interpret, or even misleading, since R-value testing measures total heat loss in

neg: Building-integrated photovoltaics the inner surface of the glass panes to conduct current out of the cell. The cell contains titanium oxide that is coated with a photoelectric dye. Most conventional solar cells use visible and infrared light to generate electricity. In contrast, the innovative new solar cell also uses ultraviolet radiation. Used to replace conventional window glass, or placed over the glass, the installation surface area could be large, leading to potential uses that take advantage of the combined functions of power generation, lighting and temperature control. Another name for transparent photovoltaics is “translucent photovoltaics” (they transmit half the light that falls

neg: Integrating sphere from the effects of beam shape, incident direction, and incident position, as well as polarization. The optical properties of the lining of the sphere greatly affect its accuracy. Different coatings must be used at visible, infrared and ultraviolet wavelengths. High-powered illumination sources may heat or damage the coating, so an integrating sphere will be rated for a maximum level of incident power. Various coating materials are used. For visible-spectrum light, early experimenters used a deposit of magnesium oxide, and barium sulfate also has a usefully flat reflectance over the visible spectrum. Various proprietary PTFE compounds are also used for visible

neg: Plasticulture the soil, preventing evaporation of moisture from the soil, minimization of seedtime and harvest, prevent weed growth, and to prevent erosion. Pigmented or colourless films can be used, each with specific advantages and disadvantages over the other. Black films prevent weed growth, but do not transmit light to heat up the soil; clear films transmit light and heat the soil, but promote weed growth. Photosensitive films have been developed that are pigmented to prevent weed growth, but still transmit light to heat the soil. These photosensitive films are more costly than either the clear or black polyethylene sheeting. Black plastic

neg: Atheris squamigera have light-colored keels and sometimes yellow tips that form a series of 30 or more light crossbands or chevrons. On the tail, there are 10 to 19 chevrons: not always clearly defined, but usually present. The ventral edge of the dorsum has light spots in pairs. An interstitial black color is visible only when the skin is stretched. The belly is yellow or dull to pale olive; it may be uniform in color, or heavily mottled with blackish spots. The throat is sometimes yellow. The tail has a conspicuous ivory white tip, 7 to 12 mm long, extending back over

neg: Visible light communication and act to protect their eyes from damage. The history of visible light communications (VLC) dates back to the 1880s in Washington, D.C. when the Scottish-born scientist Alexander Graham Bell invented the photophone, which transmitted speech on modulated sunlight over several hundred meters. This pre-dates the transmission of speech by radio. More recent work began in 2003 at Nakagawa Laboratory, in Keio University, Japan, using LEDs to transmit data by visible light. Since then there have been numerous research activities focussed on VLC. In 2006, researchers from CICTR at Penn State proposed a combination of power line communication (PLC) and

neg: Metamaterial cloaking Before actually building the device, theoretical studies were conducted. The following is one of two studies accepted simultaneously by a scientific journal, as well being distinguished as one of the first published theoretical works for an invisibility cloak. The exploitation of "light", the electromagnetic spectrum, is accomplished with common objects and materials which control and direct the electromagnetic fields. For example, a glass lens in a camera is used to produce an image, a metal cage may be used to screen sensitive equipment, and radio antennas are designed to transmit and receive daily FM broadcasts. Homogeneous materials, which manipulate or

neg: Li-Fi which converts the light into digital information. Light emitting diodes enable the consumer product to communicate synchronously with the mobile device. Professor Harald Haas coined the term "Li-Fi" at his 2011 TED Global Talk where he introduced the idea of "wireless data from every light". He is a Chair Professor of Mobile Communications at the University of Edinburgh, and the co-founder of pureLiFi along with Dr Mostafa . The general term "visible light communication" (VLC), whose history dates back to the 1880s, includes any use of the visible light portion of the electromagnetic spectrum to transmit information. The D-Light project

neg: Patently offensive in the 1973 case "Miller v. California". It has three parts: Chief Justice Warren E. Burger, writing for the majority, included the following definitions of what may be "patently offensive": Patently offensive Patently offensive is a term used in United States law regarding obscenity under the First Amendment. The phrase "patently offensive" first appeared in "Roth v. United States", referring to any obscene acts or materials that are considered to be openly, plainly, or clearly visible as offensive to the viewing public. The "Roth" standard outlined what is to be considered obscene and thus not under First Amendment protection. The

neg: Solid and tungsten carbide. Both are valued for their abrasion resistance, and hence find use in such applications as the wear plates of crushing equipment in mining operations. Most ceramic materials, such as alumina and its compounds, are formed from fine powders, yielding a fine grained polycrystalline microstructure that is filled with light-scattering centers comparable to the wavelength of visible light. Thus, they are generally opaque materials, as opposed to transparent materials. Recent nanoscale (e.g. sol-gel) technology has, however, made possible the production of polycrystalline transparent ceramics such as transparent alumina and alumina compounds for such applications as high-power lasers. Advanced

neg: Glass and can follow surface tension, which imposes a microscopically smooth surface. These properties, which give glass its clearness, can be retained even if glass is partially light-absorbing, i.e., colored. Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it (due to the absence of grain boundaries). It is used in the manufacture of lenses and windows. Common glass has a refraction index around 1.5. This may be modified by adding low-density materials such as boron, which lowers the index of refraction (see crown glass), or increased (to as much as 1.8) with high-density materials

neg: Collections care with higher energy than visible light. It does not contribute to the accurate viewing of collections and is ideally completely eliminated; otherwise materials may be weakened in any number of ways ranging from yellowing to disintegration. Organic materials, especially textiles and paper, are particularly vulnerable to UV-caused decay. Direct sunlight holds the most potential for UV damage, but certain types of artificial light bulbs may also produce these harmful rays. Various types of filters have been developed to combat UV interaction with artifacts on display, and many of them can be used in conjunction with each other to reach the

neg: Cetus as magnitude 7. Cetus lies far from the galactic plane, so that many distant galaxies are visible, unobscured by dust from the Milky Way. Of these, the brightest is Messier 77 (NGC 1068), a 9th magnitude spiral galaxy near Delta Ceti. It appears face-on and has a clearly visible nucleus of magnitude 10. About 50 million light-years from Earth, M77 is also a Seyfert galaxy and thus a bright object in the radio spectrum. Recently, the galactic cluster JKCS 041 was confirmed to be the most distant cluster of galaxies yet discovered. The massive cD galaxy Holmberg 15A is also

neg: White chemical compounds that absorb light in the ultraviolet and violet region (usually 340–370 nm) of the electromagnetic spectrum, and re-emit light in the blue region (typically 420–470 nm). OBAs are often used in paper and clothing to create an impression of very bright white. This is due to the fact that the materials actually send out more visible light than they receive. Bleaching is a process for whitening fabrics which has been practiced for thousands of years. Sometimes it was simply a matter of leaving the fabric in the sun, to be faded by the bright light. In the 18th

neg: Zone plate are many wavelengths of light outside of the visible area of the electromagnetic spectrum where traditional lens materials like glass are not transparent, and so lenses are more difficult to manufacture. Likewise, there are many wavelengths for which there are no materials with a refractive index significantly larger than one. X-rays, for example, are only weakly refracted by glass or other materials, and so require a different technique for focusing. Zone plates eliminate the need for finding transparent, refractive, easy-to-manufacture materials for every region of the spectrum. The same zone plate will focus light of many wavelengths to different foci,

neg: Patently offensive Patently offensive Patently offensive is a term used in United States law regarding obscenity under the First Amendment. The phrase "patently offensive" first appeared in "Roth v. United States", referring to any obscene acts or materials that are considered to be openly, plainly, or clearly visible as offensive to the viewing public. The "Roth" standard outlined what is to be considered obscene and thus not under First Amendment protection. The "Roth" standard was largely replaced by the "Miller" test established by "Miller v. California" (1973). According to the "Roth Standard" a work is obscene if: The Miller test was developed

neg: Jāņi and bees. Together with Jāņi cheese and fires, wreaths are also symbols of the sun. During Jāņi, fires (also known as pūdeļa, pundeļa, Jāņi candles, and witch burning) are lit and burned from sunset till next morning. This practice reflects the belief that light from the fires will transmit to the next solar year. It is believed that fires should be burned at a high point in the landscape, from which the light of the fire bestows power and fertility on the fields and people on which it shines. Leaping over the Jāņi fire is said to bring good luck

neg: Transparent conducting film visible light passes through. Some applications, such as solar cells, often require a wider range of transparency beyond visible light to make efficient use of the full solar spectrum. Transparent conductive oxides (TCO) are doped metal oxides used in optoelectronic devices such as flat panel displays and photovoltaics (including inorganic devices, organic devices, and dye-sensitized solar cell). Most of these films are fabricated with polycrystalline or amorphous microstructures. Typically, these applications use electrode materials that have greater than 80% transmittance of incident light as well as electrical conductivities higher than 10 S/cm for efficient carrier transport. In general, TCOs for

neg: Attenuation materials at a frequency of 1 MHz are listed below: There are two general ways of acoustic energy losses: absorption and scattering, for instance light scattering. Ultrasound propagation through homogeneous media is associated only with absorption and can be characterized with absorption coefficient only. Propagation through heterogeneous media requires taking into account scattering. Fractional derivative wave equations can be applied for modeling of lossy acoustical wave propagation, see also acoustic attenuation and Ref. Shortwave radiation emitted from the sun have wavelengths in the visible spectrum of light that range from 360 nm (violet) to 750 nm (red). When the sun's

neg: Delta Goodrem driving" and features Goodrem placing her head and arms outside a moving a vehicle and "moving around in a motor vehicle with no clearly visible safety belt". In response to the complaints, Apple Inc. said that it felt "confident" that the advertisement didn't breach the Australian Association of National Advertisers (AANA) Advertiser Code of Ethics standards and saw no issues relating to car safety, with both individuals in the car wearing lap seat belts. The ASB said that people may not realise that vintage cars are fitted with lap seatbelts which are not clearly seen in the video. The advertisement

neg: Absorption (electromagnetic radiation) allows for material identification. In optics, sunglasses, colored filters, dyes, and other such materials are designed specifically with respect to which visible wavelengths they absorb, and in what proportions. In biology, photosynthetic organisms require that light of the appropriate wavelengths be absorbed within the active area of chloroplasts, so that the light energy can be converted into chemical energy within sugars and other molecules. In physics, the D-region of Earth's ionosphere is known to significantly absorb radio signals that fall within the high-frequency electromagnetic spectrum. In nuclear physics, absorption of nuclear radiations can be used for measuring the fluid levels,

neg: Ubiquitous Energy being absorbed. Developed from research done at Massachusetts Institute of Technology (MIT) they have developed organic photoactive materials (organic photovoltaics, OPVs) that allow visible light to pass through its technology but selectively absorb the light from the invisible part of the spectrum, near infrared (NIR) and ultraviolet (UV) light. They call this technology ClearView power. ClearView Power is an invisible film less than 1/1000 of a millimeter thick that can be put onto any surface and generate energy without with out affecting the material beneath it. Specifically they are trying to capture all of the photons of ultraviolet and infrared

neg: X-ray optics X-ray optics X-ray optics is the branch of optics that manipulates X-rays instead of visible light. It deals with focusing and other ways of manipulating the X-ray beams for research techniques such as X-ray crystallography, X-ray fluorescence, small-angle X-ray scattering, X-ray microscopy, X-ray phase-contrast imaging, X-ray astronomy etc. Since X-rays and visible light are both electromagnetic waves they propagate in space in the same way, but because of the much higher frequency and photon energy of X-rays they interact with matter very differently. Visible light is easily redirected using lenses and mirrors, but because the refractive index of all materials

neg: Metamaterial cloaking these materials are analogous to crystals for optics. Also, a metamaterial is composed of a sequence of elements and spacings, which are much smaller than the selected wavelength of light. The selected wavelength could be radio frequency, microwave, or other radiations, now just beginning to reach into the visible frequencies. Macroscopic properties can be directly controlled by adjusting characteristics of the rudimentary elements, and their arrangement on, or throughout the material. Moreover, these metamaterials are a basis for building very small cloaking devices in anticipation of larger devices, adaptable to a broad spectrum of radiated light. Hence, although light consists

neg: Stain Stain A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Staining is used for biochemical research, metal staining, and art (e.g., wood staining, stained glass). There can be intentional stains (such as wood stains or paint), indicative stains (such as food coloring or adding a substance to make bacteria visible under a microscope), natural stains (such as rust on iron or a patina on bronze), and accidental stains such as ketchup on a shirt. Different types

neg: Headlight covers of light that must pass through and/or the minimum distance from which a vehicle's headlights must be visible. Headlight covers Headlight covers are aftermarket modifications made from a variety of materials (e.g., metal, polycarbonate, ABS plastic or self-adhesive vinyl film) which are applied over the headlamps of a new or used car in order to reduce the percentage of light transmitted, to tint the color of the light transmitted and/or to protect the lenses from stone chips, bug splatters, pedestrians and minor abrasions. During World War II civil and military authorities often enforced brownout and blackouts which restricted the use

neg: Media-independent interface clock generated by the PHY based on the link speed (25 MHz for 100 Mbit/s, 2.5 MHz for 10 Mbit/s). The remaining transmit signals are driven by the MAC synchronously on the rising edge of TX_CLK. This arrangement allows the MAC to operate without having to be aware of the link speed. The transmit enable signal is held high during frame transmission and low when the transmitter is idle. Transmit error may be raised for one or more clock periods during frame transmission to request the PHY to deliberately corrupt the frame in some visible way that precludes it from

neg: Nidd Valley Light Railway footpath crosses the dam to the north side of the lake, where the incline to the quarry is still clearly visible. Another footpath follows the trackbed along the southern edge of Scar House Reservoir, to reach Angram dam. The course of the railway is clearly visible on the modern 1:25,000 Ordnance Survey map for almost the entire length of the railway. Nidd Valley Light Railway Nidd Valley Light Railway, was a light railway in upper Nidderdale in the West Riding of Yorkshire, England. It was owned by Bradford Corporation Waterworks Department and the Corporation also operated its public passenger services.

neg: Photon upconversion Photon upconversion Photon upconversion (UC) is a process in which the sequential absorption of two or more photons leads to the emission of light at shorter wavelength than the excitation wavelength. It is an anti-Stokes type emission. An example is the conversion of infrared light to visible light. Upconversion can take place in both organic and inorganic materials, through a number of different mechanisms. Organic molecules that can achieve photon upconversion through triplet-triplet annihilation are typically polycyclicaromatic hydrocarbons (PAHs). Inorganic materials capable of photon upconversion often contain ions of d-block or f-block elements. Examples of these ions are Ln, Ti,

neg: July 12, 2007, Baghdad airstrike that at least one man in that group was carrying a rocket-propelled grenade launcher, a clearly visible weapon that runs nearly two-thirds the length of his body. WikiLeaks also does not point out that at least one man was carrying an AK-47 assault rifle. He is seen swinging the weapon below his waist while standing next to the man holding the RPG." "The Guardian" stated "It is unclear if some of the men are armed but Noor-Eldeen can be seen with a camera". Glenn Greenwald of "Salon.com" said that "the vast majority of the men were clearly unarmed". Greenwald called

neg: Spectrophotometry of colors it can transmit through the test sample), the percentage of sample-transmission, the logarithmic range of sample-absorption, and sometimes a percentage of reflectance measurement. A spectrophotometer is commonly used for the measurement of transmittance or reflectance of solutions, transparent or opaque solids, such as polished glass, or gases. Although many biochemicals are colored, as in, they absorb visible light and therefore can be measured by colorimetric procedures, even colorless biochemicals can often be converted to colored compounds suitable for chromogenic color-forming reactions to yield compounds suitable for colorimetric analysis. However, they can also be designed to measure the diffusivity

neg: Frogfish are covered with algae or hydrozoa. Their camouflage can be so perfect, that sea slugs have been known to crawl over the fish without recognizing them. For the scaleless and unprotected frogfish, camouflage is an important defense against predators. Some species can also inflate themselves, like pufferfish, by sucking in water in a threat display. In aquaria and in nature, frogfish have been observed, when flushed from their hiding spots and clearly visible, to be attacked by clownfish, damselfish, and wrasses, and in aquaria, to be killed. Many frogfishes can change their colour. The light colours are generally yellows or

neg: DU spectrophotometer Biological molecules, including proteins and nucleic acids, absorb light energy in both the ultraviolet and visible range. The spectrum of visible light was not broad enough to enable scientists to examine substances such as vitamin A. Accurate characterization of complex samples, particularly of biological materials, would require the accurate reading of absorption frequencies in the ultraviolet and infrared (IR) sections of the spectrum in addition to visible light. Existing instruments such as the Cenco "Spectrophotelometer" and the Coleman Model DM Spectrophotometer could not be effectively used to examine wavelengths in the ultraviolet range. The array of equipment needed to measure

neg: Wafer bond characterization transmitted light. The IR light is able to illuminate the crack, when using materials transparent to IR or visible light. If the fracture surface toughness is very high, it is very difficult to insert the blade and the wafers are endangered to break at the slide in of the blade. The DCB test characterizes the time dependent strength by mechanical fracture evaluation and is therefore well suited for lifetime predictions. A disadvantage of this method is, that between the entering of the blade and the time to take the IR image, the results can be influenced. In addition, the measurement

neg: PET bottle recycling are filled with water and left in the sun to allow disinfection by ultraviolet radiation. PET is useful for this purpose because many other materials (including window glass) that are transparent to visible light are opaque to ultraviolet radiation. A novel use is as a building material in third-world countries. According to online sources, the bottles, in a labor-intensive process, are filled with sand, then stacked and either mudded or cemented together to form a wall. Some of the bottles can be filled instead with air or water, to admit light into the structure. PET bottle recycling Bottles made of

neg: Dispersive prism prism led Sir Isaac Newton to conclude that light consisted of a mixture of different colors, which when combined could appear "white." Although the refractive index is dependent on the wavelength in every material, some materials have a much more powerful wavelength dependence (are much more dispersive) than others. Crown glasses such as BK7 have a relatively small dispersion, while flint glasses have a much stronger dispersion (for visible light) and hence are more suitable for use as dispersive prisms. Fused quartz and other optical materials are used at ultraviolet and infrared wavelengths where normal glasses become opaque. The top

neg: Civilizations in Babylon 5 realizing how they are being used. They also have the same light distortion/phasing ability that the Shadows have, although whether this is due to technology or a natural ability was never stated. They are clearly sentient, as the individual seen in the episode "The Long Dark" was able to board a ship and reprogram its computer, and they are very patient. They are not invincible, however. If they can be tricked into becoming partially visible, they can be killed by multiple heavy PPG blasts at point-blank range. According to JMS in "The Lurker's Guide to Babylon 5": "[This species is]

neg: Conservation and restoration of paintings the sides to show the small cracks and surface texture clearly. UVF- Ultraviolet Fluorescence- Lighting the painting with ultraviolet radiation to resulting in fluorescent glowing from the varnishes and previous conservation. IRR-Infrared Reflectography- when the painting is exposed to infrared radiation and its reflection is recorded. The underpainting or drawing of the painting will become visible with IR radiation. IRFC- Infrared False Color- When the visible image and infrared image are overlapped to view the areas of different material usage and retouches. IRF-Infrared Fluorescence- The painting is exposed to both visible light and infrared light causing particular pigments to fluoresce

neg: Translucent concrete much coarser light pattern are available. The main advantage of these products is that on large scale objects the texture is still visible — while the texture of finer translucent concrete becomes indistinct at distance. Further pictograms and lettering can be realized with this technology. An approach that does not use waveguides involves using transparent aggregate and binders. However, chemically this would not necessarily resemble concrete, and might resemble fiberglass. Unlike materials requiring alignment of optical fibers, however, it might be transported and poured using existing infrastructure. Translucent concrete Translucent concrete (also: light-transmitting concrete) is a concrete based building material

neg: Preservation (library and archival science) has a significant effect on materials. It is not only the light visible to humans that can cause damage, but also ultraviolet light and infrared radiation. Measured in lux or the amount of lumens/m, the generally accepted level of illumination with sensitive materials is limited to 50 lux per day. Materials receiving more lux than recommended can be placed in dark storage periodically to prolong the original appearance of the object. Recent concerns about the impact of climate change on the management of cultural heritage objects as well as the historic environment has prompted research efforts to investigate alternative climate

neg: Light-emitting diode into a lower energy level and releases energy in the form of a photon. The wavelength of the light emitted, and thus its color, depends on the band gap energy of the materials forming the "p-n junction". In silicon or germanium diodes, the electrons and holes usually recombine by a "non-radiative transition", which produces no optical emission, because these are indirect band gap materials. The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible, or near-ultraviolet light. LED development began with infrared and red devices made with gallium arsenide. Advances in materials science

neg: Dental curing light the quartz-halogen bulb; this device had longer wavelengths of the visible light spectrum and allowed for greater penetration of the curing light and light energy for resin composites. The halogen curing light replaced the UV curing light. The 1990s presented great improvements in light curing devices. As dental restorative materials advanced, so too did the technology used to cure these materials; the focus was to improve the intensity in order to be able to cure faster and deeper. In 1998 the plasma arc curing light was introduced. It uses a high intensity light source, a fluorescent bulb containing plasma, in

neg: HD 177830 HD 177830 HD 177830 is a 7th magnitude binary star system located approximately 205 light-years away in the constellation of Lyra. The primary star is slightly more massive than our Sun, but cooler being a type K star. Therefore, it is a subgiant clearly more evolved than the Sun. In visual light it is four times brighter than the Sun, but because of its distance, about 205 light years, it is not visible to the unaided eye. With binoculars it should be easily visible. The primary star is known to have two extrasolar planets orbiting around it. The secondary star

neg: Fluoroscopy thus image contrast) into a form that is visible. Classic film-based radiography achieves this by the variable chemical changes that the X-rays induce in the film, and classic fluoroscopy achieves it by fluorescence, in which certain materials convert X-ray energy (or other parts of the spectrum) into visible light. This use of fluorescent materials to make a viewing scope is how fluoroscopy got its name. As the X-rays pass through the patient, they are attenuated by varying amounts as they pass through or reflect off the different tissues of the body, casting an X-ray shadow of the radiopaque tissues (such

neg: Kitsunebi combusts above 60 degrees, which would also be a reason for why the fox's true identity would be linked to the light from phosphorus. However, the kitsunebi in legends is said to be visible even from a distance of several kilometers away, which would be hard to square with the idea that they are actually sources of light as weak as hypha or phosphorus. In 1977, the folkloricist Yoshiharu Tsunda's detailed research gave the explanation that almost all kitsunebi can be explained by a large refraction of light that often occurs in alluvial fans that go between mountainous and plains

neg: Lens (optics) Lens (optics) A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses ("elements"), usually arranged along a common axis. Lenses are made from materials such as glass or plastic, and are ground and polished or molded to a desired shape. A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Devices that similarly focus or disperse waves and radiation other than visible light are also

neg: Zero waste be crushed. Brick, wood and stone are among the oldest truly recyclable materials used in construction. A historic review of old buildings, barns and bridges clearly shows that brick, stones and timber are reused from older buildings. Some of the oldest structures on the planet are built with materials that were recycled from previous structures. One recent example is the Mayflower Barn at Jordans just north of High Wycombe, UK. The barn is clearly built of reused timbers, possibly sourced from the salvage of the Mayflower ship. It is simply a fact of life that historically materials that could be

neg: Nebula they are extended and contain no well-defined boundaries. Diffuse nebulae can be divided into emission nebula, reflection nebulae and "dark nebulae." Visible light nebulae may be divided into emission nebulae that emit spectral line radiation from excited or ionized gas (mostly ionized hydrogen); they are often called HII regions (the term "HII" refers to ionized hydrogen). Reflection nebulae are visible primarily due to the light they reflect. Reflection nebulae themselves do not emit significant amounts of visible light, but are near stars and reflect light from them. Similar nebulae not illuminated by stars do not exhibit visible radiation, but may