Revise GCSE Physics


Question:How does a CD work?

Diagram explaining how a CD stores information and how that information is read by a laser.

The bottom of a CD is shiny because it is a plastic protective layer over a reflective metal layer.

In the metal layer a series of pits are created in a circular pattern.

A laser beam is focussed to a small spot and then scanned across the surface of the disc.

The laser is not reflected to the detector when it hits a pit and so a pattern of on and off signals is recorded by the detector as the laser scans across a series of pits and the spaces between the pits (called lands).

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