Producing Light Waves


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Producing Light Waves

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