Q11DQ Information is stored on an audi... [FREE SOLUTION]

91影视

University Physics with Modern Physics

Hugh D. Young, Roger A. Freedman

Physics

14th edition Edition 路 1596 pages

ISBN: 9780321973610

Chapter 5: Q11DQ (page 1211)

Information is stored on an audio compact disc, CD-ROM, or DVD disc in a series of pits on the disc. These pits are scanned by a laser beam. An important limitation on the amount of information that can be stored on such a disc is the width of the laser beam. Explain why this should be, and explain how using a shorter wavelength laser allows more information to be stored on a disc of the same size.

Short Answer

Expert verified

Using a shorter wavelength, the diffraction angle is less. This allows much finer and larger number of pits to be drawn on the disk. Hence, storing more information.

Step by step solution

Given Data

A compact disc stores information in a series of pits which are scanned by a laser beam when put in a CD player. The information is escorted from the storage with the help of diffraction of the laser beam.

Information stored in CD or DVD

According to the equation

${蝉颈苍胃}_{m} = \frac{尘位}{a}$

Where $位$ is the wavelength of the laser, = width of the beam, $胃_{m}$ = angle of diffraction, and m is an integer other than zero.

With shorter wavelength, it is possible to detect finer pits since the diffraction angle will be smaller. Thus, more information can be stored at the particular size disc.

But if we further reduce the wavelength, after a certain point the frequency will be so high that the laser might burn the disc, which ultimately limits the information that can be stored by the disc.