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Reading a CD
The information
is stored on a CD digitally, as a sequence of 1s and 0s.
On the surface of a conventional CD this is represented
by a continuous, microscopic track of bumps and flat areas
that spirals out from the centre of the disc. An average
disc is only 12 cm in diameter but the spiral of data
can stretch up to 5 km in length! |
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Reading
a 1 and 0

Images adapted from www.howstuffworks.com |
To read the CD a laser follows the spiral track.
As the laser passes over a flat area the light bounces
back into an optical sensor which reads a binary
1. When the laser reaches a bump the light is reflected
away form the sensor and a binary 0 is registered. |
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