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.