Optical Storage Devices (CD's, DVD's and Blu-Ray)

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Optical storage devices such as CD's and DVD's are polymer discs which contain data similar to Magnetic with 1's and 0's though these are more commonly referred to "Pits" and "Lands". The discs are read using an Optical laser which sends a beam of light into the section of the disc, weather the light comes back again defines if its a 0 or a 1.

Since the introduction of Optical technology scientists have invented dual layer discs. This is simply 2 disc on top of each other doubling the overall capacity. The laser reads the each layer by changing the frequency of the laser so for example if it wanted to read the bottom layer then the laser would make itself strong enough to get through the first but stop at the second so that it can read the bottom disc.

There are several different types of optical storage:

DVD
DVD stands for Digital Versatile/Video Disc, There are 2 main types of DVD; DVDR (rwritable) and DVDRW (ReWritable). DVD's can record up to 2 hours of good quality video and store up to 4.27GB.

Blu-Ray
Blu-Ray Disks were created to record, rewrite and playback High-definition (HD) video, it can also be used to store large amounts of data due to the high capacity (25GB single layer and 50GB dual layer).

CD
CD's are one of the oldest forms of optical disk technology. A CD also known as a Compact Disk and was orginaly developed to stor audio files however it can be used to store multiple other types of data. The capacity of a CD is 700MB, this is very low compared to the 50,000MB in a Dual Layer Blu-Ray disk.

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