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Asked by avengedsevenfold to David, Luna, Mark, Melanie, Probash on 21 Mar 2011 in Categories: General. This question was also asked by coreyanddaz.
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David Pyle answered on 20 Mar 2011:
These colours are due to the diffraction of light by the internal surface of the CD. Data are burned into CDs by lasers, forming a series of aligined pits which are of the order of 120 nanometres deep (1 nanometer = one billionth of a metre = 1e-9 m) and 600 nm wide, and spaced about 1200 nm apart. The regular structure of the aligned pits, and the fact that the width of the pits is close to the wavelength of light (390 – 700 nanometres, or so) means that white light arriving on the pitted surface will be diffracted, giving the iridescent (rainbow) colours observed.
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Luna Munoz answered on 21 Mar 2011:
I suppose it would be based upon the same reason we ever see rainbow colours anywhere. I think it’s the way the light hits it.
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Melanie Stefan answered on 21 Mar 2011:
Data on a CD is stored in a spiral track (similar to old LPs. Is that comparison helpful? Ask your parents if you’ve never seen an LP!) The spiral track is only 0.5 micro metres (µm) thick, which causes white light to diffract off its surface an create the rainbow colours.
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Probash Chowdhury answered on 21 Mar 2011:
Its called defraction of light or the scattering of light. A CD has many tiny grooves cut into the recorded surface (the music is cut into these grooves by a laser in the form of even tinier notches so a laser can then read the music again). The light is scattered by the tiny grooves and white light splits into the rainbow colours when scattered.
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