Audio Compact Disc Apr 2026
: A thin coating of aluminum (or gold) reflects the laser beam used for reading.
: A film of acrylic lacquer seals the reflective layer to prevent corrosion and physical damage. How It Works
: Microscopic depressions called pits and flat areas called lands are pressed into the plastic.
: A 1.2 mm thick layer of clear polycarbonate plastic .
CD players use a to scan the disc from the center outward along a spiral track. When the laser hits a pit , it scatters the light; when it hits a land , the light is reflected back to a sensor. The sensor translates these light changes into electrical signals (zeros and ones), which are then converted back into high-fidelity audio. The Compact Disc: An Introduction