How CD's and CD-R discs work

CD-R disks or CD's are an every day appliance, there used on the radio station there also used with video games, But how do they work? CD's are a thin polycarbonate disk with a thin layer of aluminum (Al) on top. CD's use strips that go around the inner circle of the disk that acts like an old vinyl record but it has data in it. So lets zoom in on the strip the strip has flat reflective areas and non-reflective bumps and the single spiral of data. The CD drive shines a laser at the disk that can detect the reflective and non-reflective surfaces. The drive then converts the reflections into 1's and 0's, binary code to read the digital data on the disk. CD-R disks can be "Burned" or "Modified" because they have an extra layer of Aluminum, Gold or green dye. The drive changes the reflections of the layer by burning into it. This layer is extremely sensitive to light so avoid exposing CD-R disks to sunlight.  

CD  

CD-R

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http://www.dma.co.nz/word/cds-what-are-they/