Special Sub-Topic: Compact Discs (CDs)
|How big is the standard CD?|
|Approximately how many minutes of music can be stored on a CD?|
|How many tracks of data are on a CD?|
1 & one. Trick question! It's one track, 0.5 microns wide, that spirals from hub to edge.
|In what 'direction' is data stored on a CD?|
inside to outside. A CD has a single spiral track of data, circling from the inside of the disc to the outside. The fact that the spiral track starts at the center means that the CD can be smaller than 12 centimeters if desired, and in fact there are now plastic baseball cards and business cards that you can put in a CD player. CD business cards hold about 2 megabytes of data before the size and shape of the card cuts off the spiral. (From 'HowStuffWorks')
|If the data track of a CD were stretched out in a line, how long would it be?|
|For standard music replay, how fast does a CD spin when being read?|
200 - 500 rpm. The drive motor is precisely controlled to rotate between 200 and 500 RPM depending on which track is being read.
|Which of the following substances is NOT a part of a CD?|
trimethylxanthine. A CD is a fairly simple piece of plastic, about 1.2 millimeters thick. Most of a CD consists of an injection-molded piece of clear polycarbonate plastic. During manufacturing, this plastic is impressed with microscopic bumps arranged as a single, continuous, extremely long spiral track of data. We will return to the bumps in a moment. Once the clear piece of polycarbonate is formed, a thin, reflective aluminum layer is sputtered onto the disc, covering the bumps. Then a thin acrylic layer is sprayed over the aluminum to protect it. The label is then printed onto the acrylic. (BTW, trimethylxanthine is also known as caffeine.)
|How thick is a CD?|
|Approximately how many bytes of data can be stored on a CD?|
0.75 gigabytes. A CD can store up to 74 minutes of music, so the total amount of digital data that must be stored on a CD is: 44,100 samples per channel per second * 2 bytes per sample * 2 channels * 74 minutes * 60 seconds per minute = 783,216,000 bytes
|What is used to read the data off of the data track of a CD?|
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