Transcription: To play back the information on a CD or CD-ROM disk, a very narrow laser beam is used to strike the microscopic pits or depressions and the flat areas called lands on the disk. When the laser beam hits a pit, the beam is diffused and not reflected back to the photodiode. When the laser beam hits a land, the beam is reflected back to the photodiode. The off and on signals passed on by the photodiode are then processed in ways that cause the display of sound, images or text.
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