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“Sources of Light ”

“Sources of Light ”. Fire – “rapid oxidation of a combustible material” – heat and light are emitted in the process Flame – visible light-emitting part of a fire – complete combustion → blue color – incomplete combustion → yellow color. yellow flame, air closed 900 °C …

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“Sources of Light ”

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  1. “Sources of Light” • Fire – “rapid oxidation of a combustible material” • – heat and light are emitted in the process • Flame – visible light-emitting part of a fire • – complete combustion → blue color • – incomplete combustion → yellow color yellow flame, air closed 900 °C … (5) blue flame, air open 1600 °C Bunsen burner Bunsen burner flames Dr. Mike Nofziger 2010

  2. “Sources of Light” Flames from a charcoal fire 750-1200 °C Candle flame 1100 °C • Incandescence is the emission of visible light from a hot body due to its temperature. • – means “to glow white” • – heat and light are emitted in the process • – incomplete combustion → yellow color Dr. Mike Nofziger 2010

  3. “Sources of Light” • Incandescence produces a blackbody spectrum of energy: • – described by the Planck function • – light output is only a function of temperature, T • – the higher T, the more light out • – the higher T, the peak shifts to the blue • – our SUN (T=6000K) and stars are “perfect” blackbody • radiators Dr. Mike Nofziger 2010

  4. “Sources of Light” • Tungsten (“Incandescent”) Light Bulbs • – tungsten filament • – resistive to the flow of electrical current • – electrical energy converted to thermal energy • – filament heats up, incandesces (emits light) Dr. Mike Nofziger 2010

  5. “Sources of Light” • Tungsten (“Incandescent”) Light Bulbs Incandescent Light Bulb 1700-3000 °C “A19” style, Edison base Dr. Mike Nofziger 2010

  6. “Sources of Light” • Automotive Incandescent Light Bulbs Dome Light H3 H4 P21 R5W P27 Sealed Beam Non-Sealed Beam Dr. Mike Nofziger 2010

  7. “Sources of Light” • Tungsten-halogen Light Bulbs • – tungsten filament • – trace amount of halogen vapor, iodine or bromine • – bulb made of fused quartz, >1atm pressure • – tungsten deposited back onto the filament • (halogen cycle) • – longer lifetime of the filament Tungsten-halogen Bulb 2500-3100 °C filament 400-1000 °C bulb wall Dr. Mike Nofziger 2010

  8. “Sources of Light” • Tungsten bulbs: Light output • – watts or lumens? • – we “see” lumens, not watts New labeling by 2011 “Brightness” Dr. Mike Nofziger 2010

  9. “Sources of Light” • Tungsten bulbs: Light output • – a 100W light tungsten bulb converts only 10W into • visible light • – 90 watts are “wasted” as heat • – need more efficient sources of light • – the sale of tungsten light bulbs will be banned in • the US by the year 2014 ?  or LED Dr. Mike Nofziger 2010 CFL

  10. “Sources of Light” • LED – Light Emitting Diode • – solid-state, semiconductor p-n junction • – GaAs, AlGaAs, GaP, AlGaInP, GaN, InGaN,etc. • – White light : Blue or UV diode w/ yellow phosphor • – 3mm, 5mm, or 8mm dia. plastic packages • Low-Power LED’s • 1-20mA of electrical current • “on/off indicators” • High-power LED’s •  500mA to >1A • Lumileds, Osram, Cree • Lighting!! • Replace incandescent bulbs Dr. Mike Nofziger 2010

  11. “Sources of Light” • LED – Light Emitting Diode Dr. Mike Nofziger 2010

  12. “Sources of Light” • Fluorescent Lamp—old style • - tube is typically straight, 1.5-8 ft. long • tube filled with low-pressure Hg vapor • pressure ≈ 0.3% atmospheric • inner surface coated with a fluorescent coating • use large, heavy magnetic ballasts Output spectrum of a typical “cool-white” lamp Dr. Mike Nofziger 2010

  13. “Sources of Light” • Compact Fluorescent Lamp “CFL”—new style • - tube is a shaped in a spiral • inner surface coated with a fluorescent coating • use lightweight, electronic ballast • standard Edison screw base (replaces light bulbs) • long-term cost savings compared to tungsten light bulbs • very little heat produced compared to tungsten light bulbs • lifetime depends on how you use it…. ? Dr. Mike Nofziger 2010

  14. “Sources of Light” • Arc Lights • 2 electrodes separated by a small gap containing a gas • flow of electricity between the electrodes ionizes the gas • light produced from the ionized gas • Carbon-rod electrodes, air gap, no glass housing: • → “Carbon Arc Lamp” (no longer used, historical) • “arch” “arc” • Tungsten electrodes, quartz envelope, gas: • neon, argon, xenon, krypton, mercury, metal halide • → “High Intensity Discharge (HID) Lamps” Dr. Mike Nofziger 2010

  15. “Sources of Light” • Type of HID Lamps 15 kW xenon arc lamp used in the IMAX projection system Mercury arc lamp used in a fluorescence microscope Automotive headlights Commercial lighting Dr. Mike Nofziger 2010

  16. “Sources of Light” • Comparison of light output: Dr. Mike Nofziger 2010

  17. “Sources of Light” • Automotive LED Headlamp Design Dr. Mike Nofziger 2010

  18. “Sources of Light” Automotive LED Headlamps !!!!! Toyota Prius Ichikoh Industries (AFS) system Lexus LS 600h Dr. Mike Nofziger 2010

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