٢٦/٠١/١٤٣١ ١Dr. Farid M. Abdel-Rahim

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٢

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٣

On a compact disc, audio information is stored in a series of pits and flat areas on the surface of thedisc. The information is stored digitally, and the alternations between pits and flat areas on the surfacerepresent binary ones and zeroes to be read by the compact disc player and converted back to soundwaves. The pits and flat areas are detected by a system consisting of a laser and lenses. The length of acertain number of ones and zeroes is the same everywhere on the disc, whether the information is nearthe center of the disc or near its outer edge. In order that this length of ones and zeroes always passesby the laser–lens system in the same time period, the linear speed of the disc surface at the location ofthe lens must be constant. This requires, according to Equation 10.10, that the angular speed vary asthe laser–lens system moves radially along the disc. In a typical compact disc player, the disc spinscounterclockwise (Fig. 10.6), and the constant speed of thesurface at the point of the laser–lens systemis 1.3 m/s. (a) Find the angular speed of the disc in revolutions per minute when information is beingread from the innermost first track ( r = 23 mm) and the outermost final track (r = 58 mm).

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٤

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٥

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٦

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٧

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٨

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ٩

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ١٠

٢٦/٠١/١٤٣١ Dr. Farid M. Abdel-Rahim ١١