Why is a DVD able to store 4.3GB of data even though it is the size of a normal CD?

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Single layer recordable DVD's can store 4.3GB of data. Data is stored on CD's and DVD's via reflective and non reflective pits on the surface of the media. These "dots" are much smaller on DVD's which gives you more room to store information on the surface of the disc.

Answer

Also because it is dual layer

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Dual Layer DVDs hold 8.5GB

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The pits on a DVD are much smaller and closer together than those on a CD. The new BlueRay disks can pack the pits even closer together because the blue light used to read them has a smaller wavelength and hence is able to resolve smaller details on a disks surface. CDs are read by a red or infrared light which has a much longer wavelength and is not able to resolve smaller pits on a disks surface.

Answer

In all cds and dvds the magneto optic effect is used to encode data. In these media piths are made by applying a high power laser onto the surface of the media. DVDs however use an advanced algorithm to compress the code and use space more efficiently.

A magneto-optic effect is any one of a number of phenomena in which an electromagnetic wave interacts with a magnetic field, or with matter under the influence of a magnetic field. The most important magneto-optic effect is the Faraday effect, in which the plane of polarization is rotated under the influence of a magnetic field parallel to the direction of propagation. This effect may be used to modulate a lightwave, and is used to make Faraday rotators and optical isolators.

In particular, in a magneto-optic material the presence of a magnetic field (either externally applied or because the material itself is ferromagnetic) can cause a change in the permeability tensor ¦Å of the material. The ¦Å becomes anisotropic, a 3¡Á3 matrix, with complex off-diagonal components, depending of course on the frequency ¦Ø of incident light¡ªsuch a permeability is sometimes called gyromagnetic. If the absorption losses can be neglected, ¦Å is a Hermitian matrix. The resulting principal axes become complex as well, corresponding to circularly-polarized light where left- and right-circular polarizations can travel at different speeds (analogous to birefringence). This leads to the Faraday effect, breaks time reversal symmetry (at least locally), and allows devices such as optical isolators to be constructed

First answer by TuRtLeHeRmIt. Last edit by Caoimhin. Contributor trust: 143 [recommend contributor]. Question popularity: 122 [recommend question]