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Producing Light Waves
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Producing Light Waves

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  • 1. Producing Light Waves
    Page 84
  • 2. 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 light
    Sun, stars, burning wood, light bulb…
    Spectroscope – Measure Light
    84
  • 3. Incandescent Lights
    A light bulb with a filament inside that glows when hot
    Invented by Thomas Edison 1879
    84
  • 4. Ordinary Light Bulbs
    Thin wire = Tungsten
    When hot glows white
    To prevent burning sealed in glass
    Nitrogen and Argon
    Less than 10% of energy used to make light
    90% of energy makes heat (infrared rays)
    85
  • 5. Tungsten-Halogen Bulb
    Thin wire = Tungsten
    When hot glows white
    To prevent burning sealed in glass
    Halogen gas
    Burns much hotter therefore more light
    Also means much more heat
    Severe fire danger
    85
  • 6. Fluorescent Lights
    Glass tube filled with mercury vapor
    Electricity causes gas to release ultraviolet rays
    Powder lines the inside of the tube
    Powder hit with UV light then releases visible light
    Advantage
    Most light created is visible light (more efficient)
    Do not get as hot as regular bulbs
    Lasts longer
    86
  • 7. Vapor Lights
    Bulbs with neon/argon gas
    Mixed with small about of solid sodium/mercury
    Electricity is used to heat gas
    Hot gas converts solid into gas which glows
    Sodium solid = Yellowish light
    Mercury solid = Bluish light
    Often used as street lights/parking lots
    No filament to burn out so long lasting and efficient
    86
  • 8. Neon Lights
    Clear/colored glass tube
    Fill with gas
    Electricity causes gases to glow
    Neon = Red light
    Argon/mercury = Green/blue
    Helium = Pink
    Krypton = Violet
    87
  • 9. Wireless Communication
    Radio/TV
    Two ways to send messages
    Amplitude Modulation (AM)
    Frequency Modulation (FM)
    90
  • 10. AM
    Less energy
    Bounce off atmosphere
    Long range
    Send messages in kHz
    Range 535 – 1605
    90
  • 11. FM
    High energy
    Pass into space
    Short range
    Send messages in MHz
    Range 88 – 108
    90
  • 12. TV
    Very High Frequency (VHF)
    Range 54 – 216 MHz
    Channels 2 – 13
    Ultra High Frequency (UHF)
    Range 470 – 806 MHz
    Channels 14 - 69
    92
  • 13. Cellular Phones
    Use microwave frequencies
    Requires a network of towers for signals
    93
  • 14. Communication Satellites
    Spacecraft that orbit Earth
    Receive and send messages to ground
    94
  • 15. Satellite Phone
    Never out of range
    Very expensive requires many orbiting satellites
    94
  • 16. Satellite Television
    Distributes AM and FM signals to entire Earth
    Small dish used to collect signals from space
    Signals are often scramble to prevent theft
    Must buy descrambler to get image (box)
    95
  • 17. GPS
    Global Positioning System
    Satellites orbit at same speed as Earth turns
    Therefore can give exact location on Earth
    Use several satellites together for accuracy
    Used by military initially
    Now available in most new cars
    96
  • 18. Review
    Illuminated vs luminous
    Different Types of light bulbs
    Incandescent
    Fluorescent
    Vapor
    Neon
    AM vs FM
    Satellites
  • 19. Quiz
  • 20. Homework
    Chose one type of light bulb and describe how it works. List at least one advantage of this type of light bulb.