Multimedia education

Question

Why are one side of CDs shiny (holographic) and how does the laser read the information on the CD?

Answer

The actual data of a CD is stored on a VERY thin film of metal (the shiny part) in the form of pits or dents on the film. This thin layer of metal is bonded to plastic (and a label is added. The reflective layer of aluminum reflects laser light. The intensity of the light changes if it hits the flat part of the metal, or the dents. This intensity of light can be read as 1 or 0...basic digital information. So short story, the shiny part (not holographic, just the light reflecting off all the dents produces a rainbow effect) holds the data that is read be a laser, and the other side can be made to look like anything (shiny, dull, a label, white, whatever). Here's a great site that tells you the whole story: http://electronics.howstuffworks.com/cd.htm