DOCSLIB.ORG

Background Information on the Properties of Light We Are Exposed to Light Everyday but Do We Every Really Think About It

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Background Information on the Properties of Light We Are Exposed to Light Everyday but Do We Every Really Think About It Career Blended Mathematics Visual Media/Dramatic Arts Teacher Manual Luminosity Background Information on the Properties of Light We are exposed to light everyday but do we every really think about it. We get a tan from the light of the sun. We read a magazine from the light of a lamp. We watch a movie at a theater from the light of the movie projector. We know that if we are too far away from a light at night that it is hard to see. If we are too close to a light it is blinding. So what can we say about light? How can we describe light in mathematical and scientific terms? Does anyone ever talk about light in that way? This set of examples and exercises will answer those questions. One thing that is really neat about the American measurement of light intensity is that it is measured in candles, as in candlepower. In fact, a very old definition of candlepower is stated in terms of candles. One candlepower is the light intensity of a standard candle made of whale 1 7 wax, weighing lb of inches in diameter, and burning 120 grains per hour. 6 8 One candlepower or one candela equals the light intensity of one candle. Light cast from a candle onto an object that is one foot away is called a footcandle. The illumination of an object by a light source is measured in footcandles. We have a modern definition of light intensity that is much more precise and scientific than the old. It is given in candelas which is really just the same name as candlepower. One candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 1012 Hz , hertz, and that has 1 a radiant intensity in that directions of W , watts per steradian. 683 sr Sometimes you will see Light Intensity listed as lumens instead of candlepower and illumination referred to as lux instead of Footcandles. Lux is the European measurement of illumination based on the metric system. It is measured in lumens per square meter. Lumen gives an overall description of light intensity from a light bulb. You might not talk about footcandles that much in everyday life or among your friends but cinematographers, photographers and gaffers (movie lighting technicians) talk about footcandles all the time. When lighting a scene for a movie or lighting a fashion model for a magazine, gaffers and photographers refer to the amount of light falling on the actors, models, or objects that are to be filmed or photographed. They often refer to the light in footcandles which is an absolute measurement of light level. 16 © Copyright 2014. The Johns Hopkins University. All Rights Reserved. Career Blended Mathematics Visual Media/Dramatic Arts Teacher Manual Luminosity Another neat thing about light is how it disperses. As we mentioned above, we know that if we are too far away from a light that it is hard to see anything, but if we are too close to a light, it is blinding. So, how exactly does light disperse? It disperses with the inverse square of the distance. For example, as your distance from a light source doubles the light intensity does not fall off by half, it falls off by a fourth. If your distance triples, the light falls off by a ninth. Illumination is given in terms of light intensity per area! It’s called the Inverse Square Law. I E d 2 E is illumination, I is the light intensity of the light bulb, and d is the distance from the light bulb to an object. What do you think the units of Illumination are? Footcandles, which is candlepower per square foot. 10 ft 10 ft 10 ft © Copyright 2014. The Johns Hopkins University. All Rights Reserved. 17 Career Blended Mathematics Visual Media/Dramatic Arts Teacher Manual Luminosity Cut Out – Cookie Square This is not a projection master/transparency. Print on paper and then cut-out the square. Place on an overhead projector to project square of light. © Copyright 2014. The Johns Hopkins University. All Rights Reserved. 19 Career Blended Mathematics Visual Media/Dramatic Arts Teacher Manual Luminosity Grouping Cards 52 © Copyright 2014. The Johns Hopkins University. All Rights Reserved. Career Blended Mathematics Visual Media/Dramatic Arts Teacher Manual Luminosity © Copyright 2014. The Johns Hopkins University. All Rights Reserved. 53 .
Load more

Recommended publications
  • Energy Efficiency of Lighting Technologies... a Historical Perspective
    Energy Efficiency of Lighting Technologies... A Historical Perspective Veritas circular Super Aladdin Famos mantle Tilley pressure wick 18CP mantle 60CP lamp 120CP mantle 300CP A seasonal look back at some ‘vintage’ lights – putting energy efficiency into context By Phil Harris CEng CEnv CMgr FCIBSE MIEE MEI MCMI, Immediate Past President, SCEME Lighting Technology Timeline For thousands of years, people lived without artificial light... 15000 BC – stone & wick lamps burning animal fat 1000 BC – spout lamps burning whale oil 1000 AD – rushlights (partly peeled rush dipped in tallow) 1300 AD – dipped candles, made from tallow or beeswax 1400 AD – moulded candle invented 1700 AD – spermaceti high-grade candle (British Standard Candle*) 1700 AD – Colza (vegetable oil) lamps with flat wicks 1750 AD – paraffin wax candles 1784 AD – Argand burner (circular wick) 1800 AD – development of coal gas for lighting 1850 AD – James Young patents refining process for paraffin (shale oil) 1865 AD – invention of the Hinks Duplex oil burner 1870 AD – central draught burner with circular wick 1880 AD – development of the electric light bulb by Swan and Edison 1885 AD – invention of the Von Welsbach incandescent mantle Duplex wick 1900 AD – wick/mantle oil lamps such as Aladdin, Famos lamp 20CP 1922 AD – Tilley patented the first commercially successful pressure lamp The Standard Candle was defined in 1860... Candlepower definition and conversion factors For financial reasons and to enable fair charges to be levied, some method of comparison of light output needed to be defined, and the result was the Standard Candle. Defined in the Metropolitan Gas Act of 1860 as: “the light produced by a pure spermaceti candle weighing one-sixth of a pound (75g) and burning at a rate of 120 grains per hour (7.77g/h)”.
    [Show full text]
  • The International System of Units (SI) - Conversion Factors For
    NIST Special Publication 1038 The International System of Units (SI) – Conversion Factors for General Use Kenneth Butcher Linda Crown Elizabeth J. Gentry Weights and Measures Division Technology Services NIST Special Publication 1038 The International System of Units (SI) - Conversion Factors for General Use Editors: Kenneth S. Butcher Linda D. Crown Elizabeth J. Gentry Weights and Measures Division Carol Hockert, Chief Weights and Measures Division Technology Services National Institute of Standards and Technology May 2006 U.S. Department of Commerce Carlo M. Gutierrez, Secretary Technology Administration Robert Cresanti, Under Secretary of Commerce for Technology National Institute of Standards and Technology William Jeffrey, Director Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. National Institute of Standards and Technology Special Publications 1038 Natl. Inst. Stand. Technol. Spec. Pub. 1038, 24 pages (May 2006) Available through NIST Weights and Measures Division STOP 2600 Gaithersburg, MD 20899-2600 Phone: (301) 975-4004 — Fax: (301) 926-0647 Internet: www.nist.gov/owm or www.nist.gov/metric TABLE OF CONTENTS FOREWORD.................................................................................................................................................................v
    [Show full text]
  • Chapter 11 - Street Lighting Table of Contents
    TOC Design Manual Chapter 11 - Street Lighting Table of Contents Table of Contents Chapter 11 - Street Lighting 11A General Information 11A-1--------------------------------General Information A. General.................................................................................................................... 1 B. Industry Outlook..................................................................................................... 1 C. Iowa Code............................................................................................................... 2 D. Definitions.............................................................................................................. 4 E. References………………………………………………………………………... 7 11B Luminaires 11B-1----------------------------------Luminaires A. Lighting Sources..................................................................................................... 1 B. Light System Depreciation..................................................................................... 2 C. Luminaire Light Distribution Classifications......................................................... 3 D. References………………………………………………………………………... 8 11B-2--------------------------------LED Lighting A. LED vs. HPS Lighting............................................................................................. 1 B. LED Lighting Advantages........................................................................................ 2 C. LED Lighting Disadvantages..................................................................................
    [Show full text]
  • IN the SUPREME COURT for the STATE of NORTH DAKOTA State
    20160091 FILED IN THE OFFICE OF THE CLERK OF SUPREME COURT JUNE 16, 2016 STATE OF NORTH DAKOTA IN THE SUPREME COURT FOR THE STATE OF NORTH DAKOTA State of North Dakota, ) ) Plaintiff and Appellant, ) ) vs. ) Supreme Court No.: 20160091 ) District Court No.: 27-2015-CR-01154 Alexander Patrick, ) ) Defendant and Appellee. ) APPEAL FROM THE DISTRICT COURT OF MCKENZIE COUNTY NORTHWEST JUDICIAL DISTRICT THE HONORABLE ROBIN A. SCHMIDT BRIEF OF THE DEFENDANT-APPELLEE Jeff L. Nehring, ND ID #05410 Whit Skinner, ND ID # 08265 NEHRING LAW OFFICE, PLLC 716 2ND ST W WILLISTON, ND 58801 [email protected] 701-577-5555 Attorneys for Defendant-Appellee TABLE OF CONTENTS Table of Contents ............................................................................................................................ i Table of Authorities ....................................................................................................................... ii Statement of the Issues..................................................................................................................¶1 Statement of the Case....................................................................................................................¶4 Statement of the Facts ...................................................................................................................¶5 Standard of Review .......................................................................................................................¶6 Argument ......................................................................................................................................¶7
    [Show full text]
  • Recommended Practice for the Use of Metric (SI) Units in Building Design and Construction NATIONAL BUREAU of STANDARDS
    <*** 0F ^ ££v "ri vt NBS TECHNICAL NOTE 938 / ^tTAU Of U.S. DEPARTMENT OF COMMERCE/ 1 National Bureau of Standards ^^MMHHMIB JJ Recommended Practice for the Use of Metric (SI) Units in Building Design and Construction NATIONAL BUREAU OF STANDARDS 1 The National Bureau of Standards was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the Office of Experimental Technology Incentives Program. THE ENSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essen- tial services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics — Electricity
    [Show full text]
  • Technical Standards Board Standard
    TECHNICAL REV. STANDARDS TSB 003 MAY1999 BOARD Issued 1965-06 400 Commonwealth Drive, Warrendale, PA 15096-0001 STANDARD Revised 1999-05 Superseding TSB 003 JUN92 Submitted for recognition as an American National Standard Rules for SAE Use of SI (Metric) Units Foreword—SI denotes The International System of Units (Le Système International d’Unités). SI was established in 1960, under the Treaty of the Meter, by Resolutions and Recommendations of the General Conference on Weights and Measures (Conférence Générale des Poids et Mesures, CGPM) and the International Committee for Weights and Measures (Comité International des Poids et Mesures, CIPM) on The International System of Units. The abbreviation "SI" is used in all languages. In 1969, the SAE Board of Directors issued a directive that "SAE will include SI units in SAE Standards and other technical reports." During the ensuing several decades, SAE metric policy evolved and implementation progressed. The SAE’s current metric policy is, "Operating Boards shall not use any weights and measures system other than metric (SI), except when conversion is not practical, or where a conflicting world industry practice exists." Principal driving forces for SAE metrication were: worldwide movement to metric units; enactment of United States Federal metric legislation and the resultant national metrication activity; the international trend in industry and business throughout the world, and the growing international scope of SAE. Currently, the widespread, strong support for international standards harmonization is another key motivating factor in the global metrication movement. TSB 003 (formerly SAE J916) has been updated periodically, to reflect SAE metric policy evolution—as well as developments in the specific, formal content of SI; and in the correct, consistent usage and application of SI...which sometimes is referred to as "the modern version of the metric measurement system." The content of TSB 003 is consistent with international and U.S.
    [Show full text]
  • NOT SO SCARY LIGHTING MATH Light – the Foot-Candle
    Lighting Math NOT SO SCARY LIGHTING MATH Light – The Foot-candle 1 fc 1 foot The direct illumination from one candle placed at a distance of one foot from a surface is defined as…. 1 foot-candle (abbreviation = fc) Foot-candle is also known as a unit of light or light level. Light – The Lumen Light – The Candela 180 deg 270 deg 90 deg 1 lm Candela 0 deg The energy of light from a candle falling on a one foot square area is Distribution Curve Polar Chart One Lumen (abbreviation = lm) Distribution Curve represents the total light pattern produced by a The total amount of light coming out of the candle is approximately 13 lumens source The total amount of light coming out of 100-watt A-lamp is approximately 1650 lumens NOT DEFINED BY DISTANCE Candela is the intensity of light at any given direction. 1 Lighting Math Lumens versus Candelas Light Measurement • Lumen is an amount of ENERGY Measures the candlepower distribution of a particular • Candela is an amount of INTESITY lamp or luminaire. • Lamp output can be measured in Lumens and Information is generated in a -- Photometric report Candelas. • Fixtures alter Lumen and Candela output (Their values can only be found in Photometry Reports) Integrating SphereGonio-Photometer The Spectro-Radiometer Methods to Calculate Light Direction of Light Point-by-Point – Direct Illumination from a Fixture or Lamp • Goal of a luminaire is to put light where the user needs it • You need…. • Convenient way to classify luminaires is by the direction of light – Photometry emitted from the luminaire – Distances from Fixture or Lamp • Commission Internationale de l’Eclairage (CIE) sets up these classifications Lumen Method – Average Light Level in a Room from a Fixture • You need….
    [Show full text]
  • Howtoreadphotometrics.Pdf
    Text.wpc 4/17/03 3:19 PM Page 63 HOW TO READ PHOTOMETRICS PHOTOMETRIC INFORMATION Photometric information is provided with each fixture to assist in the lighting layout. Test Number: The photometric test number identifies the specific lamp and Lumen luminaire combination tested. Lamp Information: Identifies the lamp designation and initial lumen output. Eye Beam Spread: Lamp beam spread to 50% maximum candlepower. Candela Center Beam Candle Power (CBCP): Maximum candlepower of lamp at nadir. cd/m2 Cutoff: Cutoff of lamp and lamp image angle as given from nadir. Footcandle Spacing Criterion (SC): Mathematically classifies the maximum spacing allowed in order to maintain reasonably even illumination. Luminaire Spacing = SC x Height to Illuminated Plane PHOTOMETRIC TERMS Efficiency: Compares how much light is emitted from a luminaire; however, efficiency does not indicate the quality of light or visual comfort of a luminaire. Lumens: Luminous flux, measured in lumens (lm), is the total amount of light Luminaire Lumens produced by a source without regard to direction. The luminous flux is provided by lamp Efficiency % = manufacturers and common lumen values are included in the lamp matrix. Lamp Lumens Candela: Luminous intensity, measured in candela (cd), is the amount of light Unit LPW: Indicates total system efficacy; however, unit LPW provides no indication produced in a specific direction. Graphically, this information is compiled into polar of the light’s direction or quality. Some luminaires with a lower LPW may produce a more formatted charts that indicate the intensity of light at each angle away from 0˚ lamp axis desirable lighting effect than a luminaire with a higher LPW.
    [Show full text]
  • SI QUICK REFERENCE GUIDE: International System of Units (SI) the Modernized Metric System*
    SI QUICK REFERENCE GUIDE: International System of Units (SI) The Modernized Metric System* UNITS The International System of Units (SI) is based on seven fundamental (base) units: Base Units Quantity Name Symbol length metre m mass kilogram kg time second s electric current ampere A thermodynamic temperature kelvin K amount of substance mole mol luminous intensity candela cd and a number of derived units which are combinations of base units and which may have special names and symbols: Examples of Derived Units Quantity Expression Name Symbol acceleration angular rad/s2 linear m/s2 angle plane dimensionless radian rad solid dimensionless steradian sr area m2 Celsius temperature K degree Celsius °C density heat flux W/ m2 mass kg/m3 current A/m2 energy, enthalpy work, heat N • m joule J specific J/ kg entropy heat capacity J/ K specific J/ (kg•K) flow, mass kg/s flow, volume m3/s force kg • m/s2 newton N frequency periodic 1/s hertz Hz rotating rev/s inductance Wb/A henry H magnetic flux V • s weber Wb mass flow kg/s moment of a force N • m potential,electric W/A volt V power, radiant flux J/s watt W pressure, stress N/m2 pascal Pa resistance, electric V/A ohm Ω thermal conductivity W/(m • K) velocity angular rad/s linear m/s viscosity dynamic (absolute)(µ)Pa• s kinematic (ν)m2/s volume m3 volume, specific m3/kg *For complete information see IEEE/ASTM SI-10. SI QUICK REFERENCE GUIDE SYMBOLS Symbol Name Quantity Formula A ampere electric current base unit Bq becquerel activity (of a radio nuclide) 1/s C coulomb electric charge A • s °C
    [Show full text]
  • 2019 Military Catalog
    PROFESSIONAL-GRADE MILITARYILLUMINATION TOOLS MILITARY LINE NEW NEW NEW SIDEWINDER SIDEWINDER® SIDEWINDER® COMPACT® II SIDEWINDER® MILITARY RESCUE MILITARY BOOT TLR-7® TLR-7®A TLR-8®A TLR-8® pg. 4 pg. 5 pg. 6 pg. 7 pg. 10 pg. 11 pg. 11 pg. 12 NEW NEW TLR-1 HL® TLR-2 HL® PROTAC® PROTAC® PROTAC® 18650 USB TLR-2 HL® G TLR-6® TLR-6® NON-LASER RAIL MOUNT 1 RAIL MOUNT 2 RAIL MOUNT HL-X TL-RACKER™ BATTERY pgs. 18-19 pgs. 20-21 pgs. 20-21 pg. 22 pg. 23 pg. 23 pg. 24 pg. 25 PROTAC HL® 4 PROTAC HL® 3 PROTAC® 1L // PROTAC® 2L PROTAC® 1L-1A A PROTAC® 2AA PROTAC® 1AAA PROTAC® 2AAA pg. 30 pg. 30 pg. 31 pg. 31 pg. 32 pg. 32 pg. 33 NEW STRION® LED STRION L ED HL® STRION DS® LED STRION DS HL® SIEGE® X USB SUPER SIEGE® THE SIEGE® SIEGE® AA BANDIT® pg. 40 pg. 41 pg. 44 pg. 45 pg. 45 pg. 46 pg. 46 CLIPMATE® USB STREAMLIGHT JR.® LED THE LOGO™ KEYMATE® USB KEYMATE® NANO LIGHT® pg. 50 pg. 50 pg. 50 pg. 51 pg. 51 pg. 51 2 STREAMLIGHT.COM / 800-523 –7488 NEW NEW TLR-1® TLR-2® TLR-8® G TLR-1®s TLR-1 IR® TLR-2®s TLR-2® G TLR-VIR® ll TLR-VIR® LIGHTS pg. 12 pg. 14 pg. 14 pg. 15 pg. 15 pg. 16 pg. 16-17 NEW PROTAC® HL-X USB PROTAC®2L-X USB PROTAC HL® 5-X USB PROTAC® 90 PROTAC® HL-X PROTAC®2L-X P RO TA C HL® PROTAC HL® USB PROTAC® HPL USB PROTAC HL® 5-X pg.
    [Show full text]
  • Flashlight & Worklight Basics
    2009 Flashlight & Worklight Basics “it is important to define what you need lighting for or, to phrase it another way, what you need the light to do, in order to answer the question of which light is best.” Rob Vajko 5/29/2009 www.nationalsafetyinc.com Flashlight & Work light Basics Candlepower, Lumens, Xenon, Luminosity, LED… It can all get pretty confusing. What’s what and what’s best? Well, that all depends on a number of factors. As in most cases, it is important to define what you need lighting for or, to phrase it another way, what you need the light to do, in order to answer the question of which light is best. So we are going to attempt to try to define some terms and try to make sense of the difference available in work lights and flashlights in order to help you make the right choice. To turn a screw you need a screwdriver. To pound nails, you need a hammer. Neither can be used very well to do the job intended for the other. It’s the same with lighting. Defining the terms Candela This measurement of light intensity has been used to replace candlepower since 1948 and is slightly more than candlepower (one candlepower is equal to about 0.981 candela). Strangely enough, you will rarely see lights rated in candela. Candlepower The term “candlepower” though it still shows up on different packages is pretty much obsolete. It was originally defined as the amount of light generated by one candle weighing 1/6th of a pound and burning at a certain rate per hour.1 Thus a flashlight that is rated at 100 candlepower is thought to be a light with the intensity of 100 such candles burning at once.
    [Show full text]
  • Wja Lighting
    Lighting for seniors Senior Vision • Smaller pupils (reduced light entering the eye) • Loss of ocular transparency (scattering) • Yellowing of the ocular media • Loss of accommodation Photobiological Effects • Neuroendrocrine consequences • Vitamin D synthesis • Sleep disorders • Depression • Reduced calcium absorption Photobiological Effects • Sleep/ wake cycle requires min 200 fc • Requires 20 minutes per day out of doors..sleep disorders in 65% of nursing home residents Measuring Light “Quality” • Disability Glare • Discomfort glare • Veiling reflections • High luminance ratios Categories of visual disability • Pre-retinal scatter – normal retinas – Increases in light levels may do more harm than good by increasing the amount of light scattered in the eye Categories of visual disability • Retinal dysfunction – Acuity and contrast sensitivity reduced – Benefit from higher light levels Lighting for Pre-retinal Scatter • Disability glare • Cataracts • Provide the highest possible object contrast while limiting the total amount of light entering the eye • Simply adding fcs makes the problem worse Lighting for Pre-retinal Scatter • Control non-task light • Shield windows • Baffled luminaires • Specular surfaces avoided Lighting for Retinal Dysfunction • See IESNA recommended fc levels..use upper levels with adequate glare control Lighting Quality • Freedom from glare (disability + discomfort) • Freedom from veiling reflections • Freedom from flicker • Adaptation control Discomfort Glare: Avoid • Bright sources • Sources that are large in area
    [Show full text]