What does a CD player use to read the disc?
AnswerA laser
A focused laser beam reflects off the disc, and a sensor reads changes in the reflection.
Tech · Facts & stats
CD facts & stats
7 fact-checked facts about compact discs, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
In CD-R, what does the R stand for?
AnswerRecordable
A CD-R can be recorded once; a CD-RW is the rewritable version.
Going deeper
What is the diameter of a standard CD?
Answer12 cm
A standard CD is 120 mm across; smaller 8 cm mini CDs also exist.
A typical recordable data CD holds about how much data?
AnswerAbout 700 MB
Common CD-Rs hold about 650 to 700 MB, far less than a DVD.
What clear plastic makes up most of a CD?
AnswerPolycarbonate
A CD is a polycarbonate disc with a thin reflective metal layer and a protective lacquer.
Expert level
What kind of laser light does a CD player use?
AnswerInfrared
CD players use a laser with a wavelength of about 780 nm, just beyond visible red light.
A CD's data is stored as tiny pits. What are the flat areas between the pits called?
AnswerLands
The laser detects transitions between pits and lands, which are decoded as binary data.
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