A CD is read by focusing a 780 nm wavelength (near infrared) semiconductor laser housed within the CD player, through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected. By measuring the intensity change with a photodiode, the data can be read from the disc. In order to accommodate the spiral pattern of data, the semiconductor laser is placed on a swing arm within the disc tray of any CD player. This swing arm allows the laser to read information from the centre to the edge of a disc, without having to interrupt the spinning of the disc itself. COUNT 5
QSN1 Where is the semiconductor laser found in a CD player? ANS1 on a swing arm QSN2 What wavelenght is used to pull data from a CD? ANS2 780 nm QSN3 What is used to discern the change of intensity in light on a CD? ANS3 photodiode QSN4 In what pattern is data stored on a CD? ANS4 spiral QSN5 What createds the change in light reflected off of a CD? ANS5 change in height between pits and lands