Context: 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.

Question: Where is the semiconductor laser found in a CD player?
Answer: on a swing arm

Question: What wavelenght is used to pull data from a CD?
Answer: 780 nm

Question: In what pattern is data stored on a CD?
Answer: spiral

Question: What is used to discern the change of intensity in light on a CD?
Answer: photodiode

Question: What createds the change in light reflected off of a CD?
Answer: change in height between pits and lands

Question: How long is the swing arm?
Answer: Unanswerable

Question: How many layers of polycarbonate are there?
Answer: Unanswerable

Question: Why is the data arranged in a spiral pattern?
Answer: Unanswerable

Question: Where is the photodiode?
Answer: Unanswerable

Question: What does the width of a pit indicate?
Answer: Unanswerable