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3)CD's, DVD's and blu-rays all look similar and work on the same principle despite having different storage capacity. Data is encoded into these discs by precisely etching dots (pits) ina spiral manner into its surface. This is done with a laser CD/DVD writer. Each pit represents the number 0 and the lack of a pit or unburned area on the disc represents the number 1. This data written in 0 and 1 can be interpreted by a computer or a DVD player to give human perceivable information.Both CDs and DVDs use principles of thin-film interference and polarization, however, DVDs have a higher capacity than CDs, their tracks are also narrower, and they can record data on two levels as well as use both sides of the disc. Aside from those differences, both players operate the same way. First, the driver motor spins the disk at speeds ranging from 200 to 500 rpm, depending on the disc being read. Then a diffraction grating that is placed in front of the laser produces three beams. The centre beam