How does a disc work?
Answer:
A Compact Disc is made from a 1.2 mm thick disc of almost pure polycarbonate plastic and weigh approximately 16 grams.
A thin seam of Super Purity Aluminium (or rarely gold ingots, used for its data longevity, such as within some limited-edition audiophile CDs) is applied to the surface to make it reflective, and is protected by a picture of lacquer.
The lacquer is normally printed directly and not near an adhesive sign. Common printing methods for compact discs are screen-printing and offset printing. compact disc data is stored as a series of tiny indentations (pits), encoded contained by a tightly packed spiral track moulded into the top of the polycarbonate stratum.
The areas between pits are known as 'lands'. Each pit is approximately 100 nm philosophical by 500 nm wide, and vary from 850 nm to 3.5 m in length.
The spacing between the tracks, the pitch, is 1.6 ?m. A disc is read by focusing a 780 nm wavelength semiconductor laser through the bottom of the polycarbonate layer. The difference surrounded by height between pits and lands lead to a phase difference between the light reflect from a pit and that from its surrounding land.
By measure the intensity with a photodiode, it is possible to read the facts from the disc. The pits and lands themselves do not directly represent the zero and ones of binary data. Instead, Non-return-to-zero, inverted encoding is used: a redeploy from pit to land or park to pit indicates a one, while no change indicates a not anything.
This in turn is decode by reversing the Eight-to-Fourteen Modulation used in mastering the disc, and afterwards reversing the Cross-Interleaved Reed-Solomon Coding, finally revealing the raw facts stored on the disc.
Pits are much closer to the label side of a disc so that defect and dirt on the clear side can be out of focus during playback. Discs consequently suffer more damage because of defect such as scratches on the sticky label side, whereas clear-side scratches can be repaired by refill them with plastic of similar index of refraction
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Duno
a laser read the cd
Understanding the CD: Material
As discussed contained by How Analog and Digital Recording Works, a CD can store up to 74 minutes of music, so the total amount of digital notes that must be stored on a CD is:
44,100 samples/channel/second x 2 bytes/sample x 2 channel x 74 minutes x 60 seconds/minute = 783,216,000 bytes
To fit more than 783 megabytes (MB) onto a disc only 4.8 inches (12 cm) surrounded by diameter requires that the individual bytes be very small. By examining the physical construction of a compact disc, you can begin to make out just how small these bytes are.
A compact disc is a fairly simple piece of plastic, almost four one-hundredths (4/100) of an inch (1.2 mm) thick. Most of a disc consists of an injection-molded piece of clear polycarbonate plastic. During manufacturing, this plastic is impressed near microscopic bumps arranged as a single, continuous, extremely long spiral track of data. We'll return to the bumps surrounded by a moment. Once the clear piece of polycarbonate is formed, a thin, reflective aluminum deposit is sputtered onto the disc, covering the bumps. Then a thin acrylic section is sprayed over the aluminum to protect it. The label is consequently printed onto the acrylic. A cross section of a complete disc (not to scale) looks like this:
Cross-section of a disc
who cares how it works.. freshly buy a cd player or put it in ur cpu and USE it!!!!
Check this article: How Cds Work
¨As discussed within How Analog and Digital Recording Works, a CD can store up to 74 minutes of music, so the total amount of digital information that must be stored on a CD is:
44,100 samples/channel/second x 2 bytes/sample x 2 channel x 74 minutes x 60 seconds/minute = 783,216,000 bytes
To fit more than 783 megabytes (MB) onto a disc only 4.8 inches (12 cm) surrounded by diameter requires that the individual bytes be very small. By examining the physical construction of a compact disc, you can begin to recognize just how small these bytes are. ...
...The compact disc player has the opening of finding and reading the data stored as bumps on the disc. Considering how small the bumps are, the CD player is an exceptionally precise piece of equipment.... ¨
A compact disk read codes that are created by light reflecting (or not reflecting) from the disk. These codes are represented by "0" and "1". There are heaps different kinds of codes such as "American Standard Code of Information Interchange". These different codes can create (or recreate) almost anything that a computer can entail to run almost any program. There is a directory with different files and folder extensions which include the physical arrangement of where the background files begin and closing stages on the compact disk. The read (write) mechanism go to the place where the directory is located to scan that notes into the main memory. Then the read (write) device goes to doesn`t matter what part of the disk contains the notes files which are needed.
it works very much alike as an old diary, with the narrative there be the track (a groove that ran within a spiral around the disc), the track contained the sound information by varying the depth of the groove the nouns was retrieved by running a syringe through the groove and measuring the movement.
next to a CD the the groove is much smaller and the syringe that reads it is a laser spine
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