1. Compact Discs Rebecca Martin May 2005

2. The CD in General Invented in 1980s Used to hold music, data, or computer software Cheap and easy to distribute a lot of information

3. Making a CD Digital data is encoded on a master disc as bumps Changed to binary language of one and zeroes in reading Strong laser burns small holes and bumps

4. Audio CDs Smaller and have a better sound quality than phonograph records and audio tapes

5. CD-ROM's Computer data stored on this format Stands for Compact Disc- Read Only Memory 650 MB

6. Even More About CD-ROM's Can store many images that take up more memory than words Can store contents of an encyclopedia with images

7. How CDs Work: CD Player Read out system retrieves sound signal Goes to amplifier and pair of headphones

8. How CDs Work: Laser Continually moving outward from center As it moves bumps move faster past laser Works because of tangential speed

9. How CDs Work: More About the Laser Cannot be extended gaps between bumps Incredibly precise to read track

10. How CDs Work: Bumps or Pits Actually bumps on the side that the laser reads, not pits 1.6 microns away from bump on the left or right of it

11. How CDs Work: Bumps or Pits Again Bumps are 0.5 microns wide, minimum of 0.83 micron long, and 125 nanometers high Small dimensions make track very long

12. How CDs Work: Track Lifted and stretched out in straight line, would be 0.5 microns wide and 3.5 miles long Incredibly precise mechanism to read

13. How CDs Work: Drive Motor Spins the disc and controls it to rotate between 200 and 500 rpm (revolutions per minute)

14. How CDs Work: Laser and Lens System Laser and lens system focus in on and read the bumps on the CDs.

15. How CDs Work: Tracking Mechanism Tracking mechanism moves laser assembly so laser beam can follow track

16. How CDs Work: Layers Injection-molded clear polycarbonate plastic Plastic is impressed with bumps during manufacturing.

17. How CDs Work: The Layers Again Reflective aluminum Thin acrylic layer Label

18. About Me My name is Rebecca Martin. I am 13 years old and go to Hanes Middle School. I enjoy playing sports and cheering for Duke. Duke is my favorite college. My favorite sports are soccer and volleyball. I also enjoy talking to my friends and hanging out with them.

19. Bibliography “How CDs Work.” U-X-L Encyclopedia of Science. Second Edition, 2002. Marshall Brain. How CDs Work. HSW MediaNetworks. 29 April 2005.. Ian Graham. How Things Work. Italy: Facts On File.1995. David Macaulay. The New Way Things Work.Boston: Houghton Mifflin Company, 1998. How Does a CDs Work? 2004. MLK. 5 May 2005..