True or false - A laser beam lays down a thin surface of film on a disc to form a CD or DVD

Question

Physics

Trace Spence

13 March, 00:32

True or false - A laser beam lays down a thin surface of film on a disc to form a CD or DVD

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Patton · Answer 1

A laser beam lays down a thin surface of film on a disc to form a CD or DVD is true.

Explanation:

With the invention of CDs, people finally had a more reliable way of collecting music. CD players are neither mechanical nor magnetic but optical: they use flashing laser lights to record and read back information from the shiny metal discs.

CDs are made from an original "master" disc. The master is "burned" with a laser beam that etches bumps (called pits) into its surface. A bump represents the number zero, so every time the laser burns a bump into the disc, a zero is stored there. The lack of a bump (which is a flat, unburned area on the disc, called a land) represents the number one. Thus, the laser can store all the information sampled from the original track of music by burning some areas (to represent zeros) and leaving other areas unburned (to represent ones). Although you can't see it, the disc holds this information in a tight, continuous spiral of about 3-5 billion pits. If you could unwrap the spiral and lay it in a straight line, it would stretch for about 6 km (roughly 3.5 miles) ! Each pit occupies an area about two millionths of a millionth of a square meter. That's pretty tiny!