Download - Producing Light Waves
Producing Light Waves
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Terminology
Illuminated – You can see the object because of the light that bounces off of it (reflected light)Moon, planets, cars, people…
Luminous – The object creates lightSun, stars, burning wood, light bulb…
Spectroscope – Measure Light
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Incandescent Lights
A light bulb with a filament inside that glows when hot
Invented by Thomas Edison 1879
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Ordinary Light Bulbs
Thin wire = TungstenWhen hot glows whiteTo prevent burning sealed in glass
Nitrogen and ArgonLess than 10% of energy used to make light90% of energy makes heat (infrared rays)
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Tungsten-Halogen Bulb
Thin wire = TungstenWhen hot glows whiteTo prevent burning sealed in glass
Halogen gasBurns much hotter therefore more lightAlso means much more heat
Severe fire danger
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Fluorescent Lights
Glass tube filled with mercury vaporElectricity causes gas to release ultraviolet raysPowder lines the inside of the tube
Powder hit with UV light then releases visible lightAdvantage
Most light created is visible light (more efficient)Do not get as hot as regular bulbsLasts longer
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Vapor Lights
Bulbs with neon/argon gasMixed with small about of solid sodium/mercuryElectricity is used to heat gasHot gas converts solid into gas which glowsSodium solid = Yellowish lightMercury solid = Bluish lightOften used as street lights/parking lotsNo filament to burn out so long lasting and efficient
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Neon Lights
Clear/colored glass tubeFill with gasElectricity causes gases to glow
Neon = Red lightArgon/mercury = Green/blueHelium = PinkKrypton = Violet
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Wireless Communication
Radio/TVTwo ways to send messages
Amplitude Modulation (AM)Frequency Modulation (FM)
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AM
Less energyBounce off atmosphereLong rangeSend messages in kHzRange 535 – 1605
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FM
High energyPass into spaceShort rangeSend messages in MHzRange 88 – 108
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TV
Very High Frequency (VHF)Range 54 – 216 MHzChannels 2 – 13
Ultra High Frequency (UHF)Range 470 – 806 MHzChannels 14 - 69
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Cellular Phones
Use microwave frequenciesRequires a network of towers for signals
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Communication Satellites
Spacecraft that orbit EarthReceive and send messages to ground
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Satellite Phone
Never out of rangeVery expensive requires many orbiting
satellites
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Satellite Television
Distributes AM and FM signals to entire EarthSmall dish used to collect signals from spaceSignals are often scramble to prevent theft
Must buy descrambler to get image (box)
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GPS
Global Positioning SystemSatellites orbit at same speed as Earth turns
Therefore can give exact location on EarthUse several satellites together for accuracy
Used by military initiallyNow available in most new cars
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Review
• Illuminated vs luminous• Different Types of light bulbs
– Incandescent– Fluorescent– Vapor– Neon
• AM vs FM• Satellites
Quiz
Homework
Chose one type of light bulb and describe how it works. List at least one advantage of this type of light bulb.