DOCSLIB.ORG

Chapter 30 Emission of Light (Sources of Light) Lecture 35

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chapter 30 Emission of Light (Sources of Light) Lecture 35 Lecture 35 Chapter 30 Emission of Light (Sources of Light) 17-Nov-10 © 2010 Pearson Education, Inc. Production of Light • Incandescent (hot) source (Stars; light bulb) – Give off continuous spectrum (all frequencies) of EM waves (electrons vibrate randomly) – Inefficient source of visual light unless temperature very high – most radiation is IR (heat) • Electrons moving between energy states in atoms, molecules, solids – Fluorescent light – Light-emitting diode (LED) – Laser Incandescence Incandescence • The frequency at which the most radiation is emitted by a hot body is proportional to its Kelvin temperature fmax ∝ T • Radiation curve of brightness versus frequency for emitted light. Spectrum of Incandescent Source Light Emission from Atomic Transitions • Light emission can be understood in terms of the “planetary” model of the atom. • Just as each element is characterized by the number of electrons that occupy the orbits or shells surrounding its atomic nucleus, each element also possesses its own characteristic pattern of electron shells, or electron energy states. • These states are found only at certain definite energies. We sometime call these allowed states electron quantum states, or Bohr orbits. © 2010 Pearson Education, Inc. Electron States in Atom – Bohr Orbits Light Emission from Electron Transition • Electrons excited to higher energy quantum state by heating or passage of electric current; drop back Photon Frequency & Energy • Emission of photon as electron de-excites • The frequency of an emitted photon ~ energy- level difference in de-exciting: E = hf © 2010 Pearson Education, Inc. Photon Energy & Frequency • The photon (quantum wave-packet of light) has an energy = difference in electron state energies • The photon frequency is related to its energy by the Planck relation: E = hf where E = energy (in Joules); f = frequency (Hz); h = Planck’s constant = 6.63 x 10-34 J/Hz • For example, transitions to the 2nd Bohr orbit in Hydrogen from higher orbits give photons with frequencies in the visible range Excitation CHECK YOURSELF Which has less energy per photon? A. Red light B. Green light C. Blue light D. All have the same. © 2010 Pearson Education, Inc. Excitation CHECK YOUR ANSWER Which has less energy per photon? A. Red light B. Green light C. Blue light D. All have the same. Explanation: In accord with E ~ f, the lowest-frequency light has the lowest energy per photon. © 2010 Pearson Education, Inc. Excitation CHECK YOURSELF Excitation is the process in which A. electrons are boosted to higher energy levels in an atom. B. atoms are charged with light energy. C. atoms are made to shake, rattle, and roll. D. None of the above. © 2010 Pearson Education, Inc. Excitation CHECK YOUR ANSWER Excitation is the process in which A. electrons are boosted to higher energy levels in an atom. B. atoms are charged with light energy. C. atoms are made to shake, rattle, and roll. D. None of the above. © 2010 Pearson Education, Inc. Emission Spectra Spectroscope • Arrangement of slit, focusing lenses, and prism or diffraction grating to see emission spectrum of light from glowing element • Each component of color is focused at a definite position according to frequency. © 2010 Pearson Education, Inc. Optical Spectrum of Hydrogen Emission Spectra Spectral lines emitted are characteristic of element © 2010 Pearson Education, Inc. Emission Spectra CHECK YOURSELF Most of what we know about atoms is gained by investigating the A. masses of elements. B. electric charge of elements. C. periodic table of the elements. D. light they emit. © 2010 Pearson Education, Inc. Emission Spectra CHECK YOUR ANSWER Most of what we know about atoms is gained by investigating the A. masses of elements. B. electric charge of elements. C. periodic table of the elements. D. light they emit. Explanation: The spectra of light emitted by atoms are © 2010 Pearson Education,considered Inc. to be the fingerprints of Absorption Spectra Absorption spectra • Atoms in a gas absorb light of the same frequency they emit. • A spectroscope can detect “dark” lines in an otherwise continuous spectrum. © 2010 Pearson Education, Inc. Absorption Spectrum of Hydrogen Fluorescence Fluorescence • Many materials excited by ultraviolet light emit visible light upon de-excitation. © 2010 Pearson Education, Inc. Fluorescence • Many substances undergo excitation when illuminated with ultraviolet light. © 2010 Pearson Education, Inc. Fluorescence • This excitation and de-excitation process is like leaping up a small staircase in a single bound, and • then descending one or two steps at a time rather than leaping all the way down in a single bound. • Photons of lower frequencies are emitted. UV light going in comes out a visible light, © 2010 Pearson Education, Inc. Fluorescence Fluorescent lamps • UV emitted by excited gas strikes phosphor material that emits white light. © 2010 Pearson Education, Inc. Fluorescence CHECK YOURSELF An atom that absorbs a photon can then emit one A. only at the same energy. B. of any energy depending on the situation. C. only at a higher energy. D. only at the same or lower energy. © 2010 Pearson Education, Inc. Fluorescence CHECK YOUR ANSWER An atom that absorbs a photon can then emit one A. only at the same energy. B. of any energy depending on the situation. C. only at a higher energy. D. only at the same or lower energy. © 2010 Pearson Education, Inc. Phosphorescence • When excited, certain crystals as well as some large organic molecules remain in a state of excitation for a prolonged period of time. • Unlike what occurs in fluorescent materials, their electrons are boosted into higher orbits and some become “stuck.” • As a result, there is a time delay between the processes of excitation and de-excitation. • Materials that exhibit this peculiar property are said to have phosphorescence. © 2010 Pearson Education, Inc. Phosphorescence • Atoms or molecules in these materials are excited by incident visible light. • Rather than de-exciting immediately, as fluorescent materials do, many of the atoms remain in a metastable state — a prolonged state of excitation— sometimes as long as several hours, although most de-excite rather quickly. • If the source of excitation is removed—for instance, if the lights are put out— an afterglow occurs while millions of atoms spontaneously undergo gradual de- excitation. • Many living creatures—from bacteria to fireflies and larger animals, such as jellyfish—chemically excite molecules in their bodies that emit light. Such living things are bioluminescent. © 2010 Pearson Education, Inc. Lamps Incandescent lamp • A glass enclosure with a filament of tungsten, through which an electric current is passed. • The hot filament emits a continuous spectrum, mostly in the infrared, with smaller visible part. • The glass enclosure prevents oxygen in air from reaching the filament, to prevent burning up by oxidation. • Argon gas with a small amount of a halogen is added to slow the evaporation of tungsten. • The efficiency of an incandescent bulb is 10% © 2010 Pearson Education, Inc. Fluorescent lamps • UV emitted by excited gas strikes phosphor material that emits white light. • About 40% efficient for visible light. © 2010 Pearson Education, Inc. Compact Fluorescent Lamp (CFL) • Miniaturize a fluorescent tube, wrap it into a coil, and outfit it with the same kind of plug a common incandescent lamp has, and you have a compact fluorescent lamp (CFL). • CFLs are more efficient than incandescent lamps, putting out about 4 times more light for the same power input. • A downside to the CFL is its mercury content, which poses environmental disposal problems. © 2010 Pearson Education, Inc. LED Lamps Light-emitting diodes (LEDs) • Monochromatic photons emitted when electrons change energy states in a solid • Low voltage source powers LED. • Very efficient at producing visible light -- about seven times better than incandescent light bulb. • Light is monochromatic, but can get white LED by combining RGB LEDs or by using blue LED + phosphorescent material © 2010 Pearson Education, Inc. Lamp Efficiency • Incandescent (hot) source (Stars; light bulb) – Only about 10% power used gives visual light – most radiation is IR (heat) – 10 lumens/Watt • Atomic transition sources – Fluorescent light – 45-50 lumens/Watt – Light-emitting diode (LED)–70 lumens/Watt Lamp Efficiency CHECK YOURSELF Which lamp is more efficient for emitting visible light? A. Incandescent lamp B. Fluorescent lamp C. Both the same for the same wattage D. None of the above. © 2010 Pearson Education, Inc. Lamp Efficiency CHECK YOUR ANSWER Which lamp is more efficient for emitting visible light? A. Incandescent lamp B. Fluorescent lamp C. Both the same for the same wattage D. None of the above. © 2010 Pearson Education, Inc. Lasers & Coherent Light Most light sources give incoherent light • Incoherent light (many frequencies and out of phase) © 2010 Pearson Education, Inc. Lasers & Coherent Light LEDs and atomic transitions can give monochromatic light • Monochromatic light out of phase © 2010 Pearson Education, Inc. Lasers Lasers can produce light that is monochromatic AND coherent • Coherent light of identical frequencies in phase © 2010 Pearson Education, Inc. Lasers • A device that produces a beam of coherent light • Many types and many ranges of light • Not a source of energy (as is sometimes thought) © 2010 Pearson Education, Inc. KeyKey PointsPoints ofof LectureLecture 3535 • Types of light sources • Incandescent source • Light emission from atomic transitions • Emission Spectra • Absorption Spectra • Fluorescence • Phosphorescence • Lamps and Lamp Efficiency • Lasers z Before Monday Nov. 29, finish Hewitt Chap. 29. z Homework #24 due by 11:00 PM Monday Nov. 29 © 2010 Pearson Education, Inc..
Load more

Recommended publications
  • Compact Fluorescent Light Bulbs
    Compact Fluorescent Light Bulbs What is a compact fluorescent lamp (CFL) bulb? A CFL bulb is a type of fluorescent bulb that screws into a standard light socket, such as a lamp or ceiling light fixture. CFLs use much less energy and last up to 10 times longer than standard light bulbs. What is in a compact fluorescent lamp (CFL) bulb? A CFL bulb is made of glass, a ceramic and metal base, a luminous powder called phosphor, and a small amount of mercury. How much mercury is contained in a CFL bulb? Manufacturers report that the amount of mercury contained in a CFL bulb is five milligrams, which is less than two ten-thousandths of an ounce. The mercury could be in the form of an invisible vapor or in a bead the size of the period at the end of this sentence. A mercury fever thermometer contains about 100 times more mercury than a CFL bulb. Is it harmful is it to be in the room where a CFL bulb has broken? The amount of mercury vapor that is released from one broken bulb is not enough to make anyone sick. However, it is best to avoid any exposure to mercury. We recommend that you ventilate the room air to the outdoors by opening a window or a door and leave the room for a few hours before cleaning up the broken bulb. How should I clean up a broken CFL bulb? It is not necessary to hire a professional to clean up the bulb. By following the directions below, you can safely clean up a broken CFL bulb.
    [Show full text]
  • Comparison of Life-Cycle Analyses of Compact Fluorescent and Incandescent Lamps Based on Rated Life of Compact Fluorescent Lamp
    Comparison of Life-Cycle Analyses of Compact Fluorescent and Incandescent Lamps Based on Rated Life of Compact Fluorescent Lamp Laurie Ramroth Rocky Mountain Institute February 2008 Image: Compact Fluorescent Lamp. From Mark Stozier on istockphoto. Abstract This paper addresses the debate over compact fluorescent lamps (CFLs) and incandescents through life-cycle analyses (LCA) conducted in the SimaPro1 life-cycle analysis program. It compares the environmental impacts of providing a given amount of light (approximately 1,600 lumens) from incandescents and CFLs for 10,000 hours. Special attention has been paid to recently raised concerns regarding CFLs—specifically that their complex manufacturing process uses so much energy that it outweighs the benefits of using CFLs, that turning CFLs on and off frequently eliminates their energy-efficiency benefits, and that they contain a large amount of mercury. The research shows that the efficiency benefits compensate for the added complexity in manufacturing, that while rapid on-off cycling of the lamp does reduce the environmental (and payback) benefits of CFLs they remain a net “win,” and that the mercury emitted over a CFL’s life—by power plants to power the CFL and by leakage on disposal—is still less than the mercury that can be attributed to powering the incandescent. RMI: Life Cycle of CFL and Incandescent 2 Heading Page Introduction................................................................................................................... 5 Background...................................................................................................................
    [Show full text]
  • Article Soot Photometer Using Supervised Machine Learning
    Atmos. Meas. Tech., 12, 3885–3906, 2019 https://doi.org/10.5194/amt-12-3885-2019 © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. Classification of iron oxide aerosols by a single particle soot photometer using supervised machine learning Kara D. Lamb1,2 1Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA 2NOAA Earth System Research Laboratory Chemical Sciences Division, Boulder, CO, USA Correspondence: Kara D. Lamb ([email protected]) Received: 15 March 2019 – Discussion started: 22 March 2019 Revised: 20 June 2019 – Accepted: 21 June 2019 – Published: 15 July 2019 Abstract. Single particle soot photometers (SP2) use laser- each class are compared with the true class for those particles induced incandescence to detect aerosols on a single particle to estimate generalization performance. While the specific basis. SP2s that have been modified to provide greater spec- class approach performed well for rBC and Fe3O4 (≥ 99 % tral contrast between their narrow and broad-band incandes- of these aerosols are correctly identified), its classification of cent detectors have previously been used to characterize both other aerosol types is significantly worse (only 47 %–66 % refractory black carbon (rBC) and light-absorbing metallic of other particles are correctly identified). Using the broader aerosols, including iron oxides (FeOx). However, single par- class approach, we find a classification accuracy of 99 % for ticles cannot be unambiguously identified from their incan- FeOx samples measured in the laboratory. The method al- descent peak height (a function of particle mass) and color lows for classification of FeOx as anthropogenic or dust-like ratio (a measure of blackbody temperature) alone.
    [Show full text]
  • Introduction 1
    1 1 Introduction . ex arte calcinati, et illuminato aeri [ . properly calcinated, and illuminated seu solis radiis, seu fl ammae either by sunlight or fl ames, they conceive fulgoribus expositi, lucem inde sine light from themselves without heat; . ] calore concipiunt in sese; . Licetus, 1640 (about the Bologna stone) 1.1 What Is Luminescence? The word luminescence, which comes from the Latin (lumen = light) was fi rst introduced as luminescenz by the physicist and science historian Eilhardt Wiede- mann in 1888, to describe “ all those phenomena of light which are not solely conditioned by the rise in temperature,” as opposed to incandescence. Lumines- cence is often considered as cold light whereas incandescence is hot light. Luminescence is more precisely defi ned as follows: spontaneous emission of radia- tion from an electronically excited species or from a vibrationally excited species not in thermal equilibrium with its environment. 1) The various types of lumines- cence are classifi ed according to the mode of excitation (see Table 1.1 ). Luminescent compounds can be of very different kinds: • Organic compounds : aromatic hydrocarbons (naphthalene, anthracene, phenan- threne, pyrene, perylene, porphyrins, phtalocyanins, etc.) and derivatives, dyes (fl uorescein, rhodamines, coumarins, oxazines), polyenes, diphenylpolyenes, some amino acids (tryptophan, tyrosine, phenylalanine), etc. + 3 + 3 + • Inorganic compounds : uranyl ion (UO 2 ), lanthanide ions (e.g., Eu , Tb ), doped glasses (e.g., with Nd, Mn, Ce, Sn, Cu, Ag), crystals (ZnS, CdS, ZnSe, CdSe, 3 + GaS, GaP, Al 2 O3 /Cr (ruby)), semiconductor nanocrystals (e.g., CdSe), metal clusters, carbon nanotubes and some fullerenes, etc. 1) Braslavsky , S. et al . ( 2007 ) Glossary of terms used in photochemistry , Pure Appl.
    [Show full text]
  • 2. Making Fires Burn Or Go out 1: Introduction to the Fire Triangle
    2. Making Fires Burn or Go Out 1: Introduction to the Fire Triangle Lesson Overview: In this activity, students describe and organize what they already know Subjects: Science, Mathematics, Writing, about fire so it fits into the conceptual model of Speaking and Listening, Health and the Fire Triangle. They examine the geometric Safety stability of a triangle and how that property Duration: one half-hour session applies to fire. Group size: Whole class. Students work in groups of 2-3. Lesson Goal: Increase students’ understanding of Setting: Indoors how fires burn and why they go out. Vocabulary: Fire Triangle, fuel, heat, ignition, oxygen, model Objectives: • Students can construct a triangle out of toothpicks and gumdrops, and can label its legs with the three components of the Fire Triangle. • Students can demonstrate that removing one side of the triangle makes it collapse. • Students can identify the component(s) of the Fire Triangle that are removed in various scenarios, and explain how this makes the fire go out. Standards: 1st 2nd 3rd 4th 5th CCSS Writing 2, 7, 8 2, 7, 8 2, 7, 10 2,7, 9, 10 2,7, 9, 10 Speaking/Listening 1, 2, 4, 6 1, 2, 4, 6 1, 2, 4, 6 1, 2, 4, 6 1, 2, 4, 6 1, 2, 3, 4, Language 1, 2, 4, 6 1, 2, 4, 6 6 1, 2, 3, 4, 6 1, 2, 3, 4, 6 MP.4, MP.4, MP.4, MP.4, Math MP.5 MP.5, MP.5 MP.5 MP.4, MP.5 Matter and Its PS1.A, NGSS Interactions PS1.B PS1.B From Molecules to Organisms: Structure/Processes LS1.C Engineering Design ETS1.B ETS1.B EEEGL Strand 1 A, B, C, E, F, G A, B, C, E, F, G Teacher Background: This activity explores the chemistry of combustion as described by a conceptual model called the Fire Triangle.
    [Show full text]
  • Energy Efficiency Lighting Hearing Committee On
    S. HRG. 110–195 ENERGY EFFICIENCY LIGHTING HEARING BEFORE THE COMMITTEE ON ENERGY AND NATURAL RESOURCES UNITED STATES SENATE ONE HUNDRED TENTH CONGRESS FIRST SESSION TO RECEIVE TESTIMONY ON THE STATUS OF ENERGY EFFICIENT LIGHT- ING TECHNOLOGIES AND ON S. 2017, THE ENERGY EFFICIENT LIGHT- ING FOR A BRIGHTER TOMORROW ACT SEPTEMBER 12, 2007 ( Printed for the use of the Committee on Energy and Natural Resources U.S. GOVERNMENT PRINTING OFFICE 39–385 PDF WASHINGTON : 2007 For sale by the Superintendent of Documents, U.S. Government Printing Office Internet: bookstore.gpo.gov Phone: toll free (866) 512–1800; DC area (202) 512–1800 Fax: (202) 512–2104 Mail: Stop IDCC, Washington, DC 20402–0001 VerDate 0ct 09 2002 11:58 Feb 20, 2008 Jkt 040443 PO 00000 Frm 00001 Fmt 5011 Sfmt 5011 G:\DOCS\39385.XXX SENERGY2 PsN: MONICA COMMITTEE ON ENERGY AND NATURAL RESOURCES JEFF BINGAMAN, New Mexico, Chairman DANIEL K. AKAKA, Hawaii PETE V. DOMENICI, New Mexico BYRON L. DORGAN, North Dakota LARRY E. CRAIG, Idaho RON WYDEN, Oregon LISA MURKOWSKI, Alaska TIM JOHNSON, South Dakota RICHARD BURR, North Carolina MARY L. LANDRIEU, Louisiana JIM DEMINT, South Carolina MARIA CANTWELL, Washington BOB CORKER, Tennessee KEN SALAZAR, Colorado JOHN BARRASSO, Wyoming ROBERT MENENDEZ, New Jersey JEFF SESSIONS, Alabama BLANCHE L. LINCOLN, Arkansas GORDON H. SMITH, Oregon BERNARD SANDERS, Vermont JIM BUNNING, Kentucky JON TESTER, Montana MEL MARTINEZ, Florida ROBERT M. SIMON, Staff Director SAM E. FOWLER, Chief Counsel FRANK MACCHIAROLA, Republican Staff Director JUDITH K. PENSABENE, Republican Chief Counsel (II) VerDate 0ct 09 2002 11:58 Feb 20, 2008 Jkt 040443 PO 00000 Frm 00002 Fmt 5904 Sfmt 5904 G:\DOCS\39385.XXX SENERGY2 PsN: MONICA C O N T E N T S STATEMENTS Page Bingaman, Hon.
    [Show full text]
  • Compact Fluorescent Lamps
    Office of Compliance fast facts advancing safety, health, and workplace rights in the legislative branch January 2009 Compact Fluorescent Lamps Environmental issues are a top priority for many Fluorescent lamps contain a organizations. These days, it's hard to watch TV small amount of mercury vapor without hearing how businesses and institutions can - approximately 5 milligrams - help the environment by "going green." One sealed within the glass tubing. increasingly popular way of contributing to the Mercury, at atmospheric pres- green movement is to install compact fluorescent sure, is a silver colored liquid lamps (CFLs), a fluorescent bulb designed to emit that tends to form balls. Mercury as much light as traditional light bulbs while using is a hazardous substance that can less energy. CFLs use about 75 percent less energy be inhaled, absorbed through the Figure 2:Burnt out CFL than standard incandescent bulbs and can last up to skin, and ingested. It is a neurotoxin that can cause - 10 times longer. CFLs also produce about 75 among many additional symptoms - tremors, insom- percent less heat, so they're safer to operate and can nia, lassitude, weight-loss, and emotional distur- cut building cooling bances. Because CFLs contain a small amount of costs. mercury, they should be recycled rather than thrown out in the trash. Fluorescent light bulbs (including compact Mercury is a critical component of CFLs and is the fluorescents) are more substance that allows the lamp to turn on. No mer- energy-efficient than cury is released when the lamps are intact or in use, regular bulbs because and if the lamp is disposed of properly, mercury in Figure 1: Compact Fluorescent Lamp of the different method CFLs shouldn't be an environmental, safety, or they use to produce health hazard.
    [Show full text]
  • Biofluorescence
    Things That Glow In The Dark Classroom Activities That Explore Spectra and Fluorescence Linda Shore [email protected] “Hot Topics: Research Revelations from the Biotech Revolution” Saturday, April 19, 2008 Caltech-Exploratorium Learning Lab (CELL) Workshop Special Guest: Dr. Rusty Lansford, Senior Scientist and Instructor, Caltech Contents Exploring Spectra – Using a spectrascope to examine many different kinds of common continuous, emission, and absorption spectra. Luminescence – A complete description of many different examples of luminescence in the natural and engineered world. Exploratorium Teacher Institute Page 1 © 2008 Exploratorium, all rights reserved Exploring Spectra (by Paul Doherty and Linda Shore) Using a spectrometer The project Star spectrometer can be used to look at the spectra of many different sources. It is available from Learning Technologies, for under $20. Learning Technologies, Inc., 59 Walden St., Cambridge, MA 02140 You can also build your own spectroscope. http://www.exo.net/~pauld/activities/CDspectrometer/cdspectrometer.html Incandescent light An incandescent light has a continuous spectrum with all visible colors present. There are no bright lines and no dark lines in the spectrum. This is one of the most important spectra, a blackbody spectrum emitted by a hot object. The blackbody spectrum is a function of temperature, cooler objects emit redder light, hotter objects white or even bluish light. Fluorescent light The spectrum of a fluorescent light has bright lines and a continuous spectrum. The bright lines come from mercury gas inside the tube while the continuous spectrum comes from the phosphor coating lining the interior of the tube. Exploratorium Teacher Institute Page 2 © 2008 Exploratorium, all rights reserved CLF Light There is a new kind of fluorescent called a CFL (compact fluorescent lamp).
    [Show full text]
  • Exterior Lighting Guide for Federal Agencies
    EXTERIOR LIGHTING GUIDE FOR FederAL AgenCieS SPONSORS TABLE OF CONTENTS The U.S. Department of Energy, the Federal Energy Management Program, page 02 INTRODUctiON page 44 EMERGING TECHNOLOGIES Lawrence Berkeley National Laboratory (LBNL), and the California Lighting Plasma Lighting page 04 REASONS FOR OUTDOOR Technology Center (CLTC) at the University of California, Davis helped fund and Networked Lighting LiGHtiNG RETROFitS create the Exterior Lighting Guide for Federal Agencies. Photovoltaic (PV) Lighting & Systems Energy Savings LBNL conducts extensive scientific research that impacts the national economy at Lowered Maintenance Costs page 48 EXTERIOR LiGHtiNG RETROFit & $1.6 billion a year. The Lab has created 12,000 jobs nationally and saved billions of Improved Visual Environment DESIGN BEST PRActicES dollars with its energy-efficient technologies. Appropriate Safety Measures New Lighting System Design Reduced Lighting Pollution & Light Trespass Lighting System Retrofit CLTC is a research, development, and demonstration facility whose mission is Lighting Design & Retrofit Elements page 14 EVALUAtiNG THE CURRENT to stimulate, facilitate, and accelerate the development and commercialization of Structure Lighting LIGHtiNG SYSTEM energy-efficient lighting and daylighting technologies. This is accomplished through Softscape Lighting Lighting Evaluation Basics technology development and demonstrations, as well as offering outreach and Hardscape Lighting Conducting a Lighting Audit education activities in partnership with utilities, lighting
    [Show full text]
  • Basic Physics of the Incandescent Lamp (Lightbulb) Dan Macisaac, Gary Kanner,Andgraydon Anderson
    Basic Physics of the Incandescent Lamp (Lightbulb) Dan MacIsaac, Gary Kanner,andGraydon Anderson ntil a little over a century ago, artifi- transferred to electronic excitations within the Ucial lighting was based on the emis- solid. The excited states are relieved by pho- sion of radiation brought about by burning tonic emission. When enough of the radiation fossil fuels—vegetable and animal oils, emitted is in the visible spectrum so that we waxes, and fats, with a wick to control the rate can see an object by its own visible light, we of burning. Light from coal gas and natural say it is incandescing. In a solid, there is a gas was a major development, along with the near-continuum of electron energy levels, realization that the higher the temperature of resulting in a continuous non-discrete spec- the material being burned, the whiter the color trum of radiation. and the greater the light output. But the inven- To emit visible light, a solid must be heat- tion of the incandescent electric lamp in the ed red hot to over 850 K. Compare this with Dan MacIsaac is an 1870s was quite unlike anything that had hap- the 6600 K average temperature of the Sun’s Assistant Professor of pened before. Modern lighting comes almost photosphere, which defines the color mixture Physics and Astronomy at entirely from electric light sources. In the of sunlight and the visible spectrum for our Northern Arizona University. United States, about a quarter of electrical eyes. It is currently impossible to match the He received B.Sc.
    [Show full text]
  • Efficient Lighting Using Compact Fluorescent Lamps and Fixtures
    APPLICATION NOTE An In-Depth Examination of an Energy Summary Efficiency Technology Compact fluorescent lamps (CFLs) can provide energy savings of up to 75 per- cent and slash maintenance costs in many common applications formerly Efficient Lighting dominated by incandescents. The chal- lenge is to obtain excellent visual qual- ity with these compact sources, as they Using Compact are often misapplied. This application note draws on the experience of lighting Fluorescent Lamps designers, manufacturers, and product users to provide guidance in how—and and Fixtures how not—to apply compact fluores- cents. CFLs come in several sizes and con- figurations, and can be applied nearly anywhere that incandescent sources are used for general area lighting. Ap- plications include ceiling downlights, task lights, wall sconces, and pendant and decorative fixtures. But even these Summary .............................................1 versatile light sources cannot be used everywhere, and they must be applied How This Technology Saves carefully to get satisfactory results. Energy .................................................1 Limitations include difficulty in dimming, Types of Compact Fluorescents.......3 the availability of lamps in sizes that fit existing fixtures, sensitivity to frequent Applicability ........................................5 on-off cycling, and low beam power be- cause of the diffuse linear light source. Field Observations to Assess In addition, lamp orientation and tem- Feasibility............................................7 perature need to be considered, since Estimation of Energy Savings ...........8 they can affect light output. Cost and Service Life .........................9 How This Technology Laws, Codes, and Regulations........10 Saves Energy Definitions of Key Terms .................10 References to More Information......11 Compact fluorescent lamps are simply miniature versions of full-sized fluores- Major Manufacturers ........................11 cents, with a few key differences.
    [Show full text]
  • Light-Emitting Diode - Wikipedia, the Free Encyclopedia
    Light-emitting diode - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Light-emitting_diode From Wikipedia, the free encyclopedia A light-emitting diode (LED) (pronounced /ˌɛl iː ˈdiː/[1]) is a semiconductor Light-emitting diode light source. LEDs are used as indicator lamps in many devices, and are increasingly used for lighting. Introduced as a practical electronic component in 1962,[2] early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet and infrared wavelengths, with very high brightness. When a light-emitting diode is forward biased (switched on), electrons are able to recombine with holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of Red, green and blue LEDs of the 5mm type 2 the semiconductor. An LED is usually small in area (less than 1 mm ), and Type Passive, optoelectronic integrated optical components are used to shape its radiation pattern and assist in reflection.[3] LEDs present many advantages over incandescent light sources Working principle Electroluminescence including lower energy consumption, longer lifetime, improved robustness, Invented Nick Holonyak Jr. (1962) smaller size, faster switching, and greater durability and reliability. LEDs powerful enough for room lighting are relatively expensive and require more Electronic symbol precise current and heat management than compact fluorescent lamp sources of comparable output. Pin configuration Anode and Cathode Light-emitting diodes are used in applications as diverse as replacements for aviation lighting, automotive lighting (particularly indicators) and in traffic signals.
    [Show full text]