Question

Hello!! I want the solution of the following question.

What is an optical disk? Explain its types like CD, DVD,Blu Ray. Please give explanation of atleast two pages.

Answer 1

Optical disk is a storage device used in computers. The storage capacity of Optical Disks is higher than the magnetic disks as it provides high recording densities. The Optical storage disks uses laser beams for ecording information.

Optical disks are circular in shape, and stores the binary data in the form of pits(binary value if 0 or Off) and land(binary value of 1 or ON).The flat surface of optical disk is made up of alminium.

The size of optical disk is between 7. 6 and 30 cms in diameter. The data on the optical diks can be recorded in three ways:

• read only e.g CD and CD ROM
• recordable
• re-recordable

Optical disks are used for storing music,videos and data .The application or types of optical disks comes in broadly three generations:

• first generation:Initially optical disks were used to store music and computer software as they were incapable of storing the video data.most of the devices of first generation had infrared laser reading head. the physical area on the disk on which the data could be stored is very less in first generation optical disks as wavelength is a limiting factor for the amount of information that can be stored. For example the maximum data that can be stored in a CD is 700 MB for a size of 12 cm compact disk. CDs come under first generation optical disks
• Second Generation: The optical disks of this generation are used to store large amounts of data including digital video. the reading takes place with the help if visible light laser preferably red.DVD is an example of second generation optical disk. The storage capacity of DVD is 4.7 Gb storage on 12 cm Compact disk.
• Third generation: the third generation optical disks will have very high storage capacity and will also store high definition video.Blue Ray is an example of Third generation optical devices. The storage capacity is 400 GB.

COMPACT DISK(CD)

Compact Disk(CD) is a digital optical disk which is used to store audio data and other data like documents,worksheets etc.Standard CDs have 120 milimeters diameter and can store opto 80 mins of recorded data or 700 MB of data.

• physical structure:A CD is made of 120mm thick polycarbonate plastic and its wieght is 15-20 grams. the components of the CD are:
  • the center spindle hole
  • the clamping ring
  • the stacking ring
  • the mirror band
  • program area(data area)
  • the ring

A thin layer of aluminium is applied to the surface in order to make it reflective.the metal is protected by a thin film of lacquer. In a CD the data is represented as tiny identations called pits.the area between the pits is called as land. The pits and lands do not directly refer to zero and one instead a change from pit to land or land to pit indicates a one and no change indicates a zero.

DVD(Digital Video Disk)

DVD is a digital video optical disk storage and is used to store any kind of digital data including softwares and digital files and videos. DVDs have the same dimensions as CD but offer a large storage space

Blue Ray Disks

Blue ray is digital video optical storage device used for storing large volumes of data including the high definition videos etc.The Blue ray disk is called by this name because of the violet laser used to read the disk, which allows the information to be stored at greater density.