Compact Discs Rebecca Martin May 2005
The CD in General Invented in 1980s Used to hold music, data, or computer software Cheap and easy to distribute a lot of information
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
Audio CDs Smaller and have a better sound quality than phonograph records and audio tapes
CD-ROM's Computer data stored on this format Stands for Compact Disc- Read Only Memory 650 MB
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
How CDs Work: CD Player Read out system retrieves sound signal Goes to amplifier and pair of headphones
How CDs Work: Laser Continually moving outward from center As it moves bumps move faster past laser Works because of tangential speed
How CDs Work: More About the Laser Cannot be extended gaps between bumps Incredibly precise to read track
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
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
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
How CDs Work: Drive Motor Spins the disc and controls it to rotate between 200 and 500 rpm (revolutions per minute)
How CDs Work: Laser and Lens System Laser and lens system focus in on and read the bumps on the CDs.
How CDs Work: Tracking Mechanism Tracking mechanism moves laser assembly so laser beam can follow track
How CDs Work: Layers Injection-molded clear polycarbonate plastic Plastic is impressed with bumps during manufacturing.
How CDs Work: The Layers Again Reflective aluminum Thin acrylic layer Label
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.
Bibliography “How CDs Work.” U-X-L Encyclopedia of Science. Second Edition, Marshall Brain. How CDs Work. HSW MediaNetworks. 29 April Ian Graham. How Things Work. Italy: Facts On File David Macaulay. The New Way Things Work.Boston: Houghton Mifflin Company, How Does a CDs Work? MLK. 5 May