{"id":7393,"key":"Lighting","title":"Lighting","latest":{"id":1210028,"timestamp":"2025-11-28T03:57:48Z"},"content_model":"wikitext","license":{"url":"https://www.appropedia.org/Appropedia:Copyrights","title":"CC-BY-SA-4.0"},"source":"{{Topic notice}}\n\n[[File:Rome (IT), Ponte Sisto -- 2013 -- 4093.jpg|thumb]]\n\n'''Lighting''' or '''illumination''' is the use of light for improving visibility at night. Lighting includes the use of both artificial light sources (ie lamps), as well as natural illumination by capturing daylight (ie using windows, skylights (sometimes makeshift with soda bottles).\n\n== What is light? ==\n\nLight is electromagnetic radiation; the human eye is sensitive to a spectrum with visible colours as seen in a rainbow. When these colours are mixed they appear as white light. More [[energy]] is present in the light of the upper or violet/blue end of the spectrum than at the red end. Therefore, more energy is generally necessary to produce the blue-violet component needed to produce what to the eye appears as white light. Therefore the quality of light (in colour terms) influences the energy requirement; if colour does not matter then it is at least theoretically more efficient to use a red or orange light, and this in fact is common practice in the case of street lighting where the most energy-efficient lights are used, namely orange/yellow sodium lights. Clearly, for domestic purposes there is merit in paying something extra to achieve a white, or near-white light.\n\nLight intensity, or illuminating power of a light source in any one direction is commonly defined in candela, which although it has a rigorous scientific definition, for practical purposes can be thought of as 'candle-power'; i.e. the output from a standard paraffin-wax candle. The rate at which light is emitted is measured in lumens, which are defined as the rate of flow of light from a light source of one candela through a solid angle of one steradian. A more easily understood approximation of this would be to imagine a one candela candle at the apex of a conical lampshade with its sides sloping at about 70 degrees to each other; the conical beam emitted, diverging at about 70 degrees, would be about one lumen.\n\n== Methods of providing light ==\n\nThere are two main physical principles by which light may be produced:\n\n* incandescent\n* fluorescent\n\nThe incandescent principle depends on heating a source to a temperature in the region of 2000, 4000 or 6000°C to obtain reddish, yellowish or white light, respectively. Typical examples are candles and lamps utilising a bright flame (where white hot or incandescent particles of carbon in the flame produce the light) and incandescent filament light bulbs where a fine coil of tungsten wire is heated (in a vacuum or inert low pressure gas to prevent the filament oxidising or burning) by an electric current passing through it. All incandescent light sources, whether flames or electrically heated filaments, tend to produce more heat than light and are therefore relatively inefficient in the rate of conversion of energy to light.\n\nFluorescence occurs under certain conditions when a material can be made to glow with a 'cold light'. Fluorescence is a phenomenon in which the atoms of a gas, vapour or solid are excited in such a way that they emit light. In some cases such as sodium and mercury vapour discharge lamps (used commonly for street lighting) vapour in a glass tube emits the light. In other cases such as the commonly used fluorescent tube lights, ultraviolet light, which is invisible to the eye, is emitted by exciting mercury vapour atoms within the tube, and this in turn causes a white translucent coating in the tube to fluoresce with a whitish light.\n\nIn other words, the coating converts invisible ultraviolet light into visible white (or near-white) light. Most fluorescent processes involve some expenditure of electrical energy, so they are accompanied by the production of some heat. (Non-electrical fluorescence is used where the mantles of pressure lamps and gas lamps are heated and emit a much brighter and whiter light than would occur simply as a result of their temperature.)\n\nFor practical purposes, the options for lighting reduce generally either to lamps that run on fuels, or electric lights. Table 1 indicates the options and their relative lighting capability.\n\n{| class=\"wikitable sortable\" border=\"1\"\n|+ align=\"bottom\" style=\"caption-side: bottom\" | Table 1: Lighting capacity\n! Type of light\n! Energy source\n! Intensity (lumens)\n! Efficiency (lumen/W)\n|-\n| Candle\n| Paraffin wax\n| 1\n| .01\n|-\n| Oil lamp (wick)\n| Kerosene\n| 1-10\n| .01-.1\n|-\n| Hurricane lamp (wick)\n| Kerosene\n| 10-100\n| .1-.2\n|-\n| Oil lamp (mantle)\n| Kerosene\n| 1000\n| 1\n|-\n| Gas lamp (mantle)\n| 1 .p.g (eg butane)\n| 1000\n| 1\n|-\n| Filament lamp 3W\n| Electricity\n| 10\n| 3\n|-\n| Filament lamp 40W\n| Electricity\n| 400\n| 10\n|-\n| Filament lamp 100W\n| Electricity\n| 1300\n| 13\n|-\n| Fluorescent 15W\n| Electricity\n| 600\n| 40\n|-\n| Fluorescent 30W\n| Electricity\n| 1500\n| 50\n|-\n| Mercury 80W\n| Electricity\n| 3200\n| 40\n|-\n| Sodium sox 35W\n| Electricity\n| 4500\n| 128\n|}\n\nMore important to the user than the efficiency in lumen/watt is the cost per lumen. Kerosene and candle wax are cheaper sources of watts than any form of electricity, and this partially makes up for their inefficiency, but not for their poor quality light (wicks) or the amount of heat. Kerosene lamps produce better light, but they are unpleasantly noisy and uncomfortably hot to be near in a tropical climate; they also use much more fuel than wick lamps, and are troublesome to start. Cylinder gas lights provide a slightly more expensive but convenient alternative.\n\n== Artificial light ==\n\nThese include [[fuel-based lighting]] and [[electric lighting]] methods. Fuel-based lighting is often far less energy efficient than combusting [[Biofuel|(bio)fuel]] in a [[Electricity generator|gen-set]] and using the electricity of this gen-set to power a electric device such as a lamp (even incandescents, and definitely using [[compact fluorescent lights]], [[LED lighting]] or LEC lighting.{{W|Light-emitting electrochemical cell}}{{Verification needed}}\n\nThat said, fuel-based lighting can be much cheaper as a short term solution owing to the set-up costs of an electricity infrastructure (whether grid power or a small scale setup of a solar panel and a battery). Poor people in the [[majority world]] hence often stick to fuel-based lighting methods. These create a lot of smoke, the amount depending on the method and fuel used, and the resulting [[indoor air pollution]] has serious negative impacts on health - causing eye and respiratory illness in particular.\n\n== Candlemaking ==\n\n{{Excerpt|Candlemaking}}\n\n== Rural lighting ==\n\n{{Excerpt|Rural lighting}}\n\n== References ==\n\n<references />\n\n[https://www.earthava.com/rise-led-lighting-technology/ LED Lighting Technology]\n\n[https://richsoil.com/CFL-fluorescent-light-bulbs.jsp Incandescent vs CFL vs LED in a Cold Climate]\n\n{{Page data\n| license = CC-BY-SA-3.0\n| keywords = photovoltaics, Technology, Construction\n| sdg = SDG07 Affordable and clean energy\n| description = Lighting affects mood, safety, and energy use. Appropedia breaks down types of lighting and how to use them efficiently.\n}}\n\n[[Category:Photovoltaics]]\n[[Category:Technology]]\n[[Category:Construction]]"}