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False colour scanning electron micrograph of the surface of a compact disc cracked to show the musical layer below (centre). The disc is made of plastic, which is pressed with a series of fine depressions (notches), representing a digitised musical signal capable of being read by a laser. To reflect the laser light, the music layer is coated with a fine film of metal (unseen) which follows the depressions exactly. This layer is covered by another layer of transparent plastic, which is visible here. The music is sandwiched between two layers of plastic, which prevents dust & scratches from affecting the sound. Magnificat- ion: x1000 at 10x8 inch size, x143 at 35mm size. Blue & red colorvir (KEYSTONE/SCIENCE PHOTO LIBRARY/DR JEREMY BURGESS.)