• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The Compact Disc

Extracts from this document...


Informattion Technology Coursework The Compact Disc Introduction The concept of the CD is based on the well-known 31/2-inch floppy disk. It is just a more complex way of storing information on a mobile piece of plastic. Today the CD has branched into all areas of modern life. Compact discs are used in music, videos, computer games and software. In this project I hope to uncover how the CD works including the mechanisms of CD drives and focus on the use of the laser in the system, all from a physicist's perspective. I also wish explain the practical benefits of the CD and why it has become so widely distributed in such a short time, and just how it has done so much for us. There seems to be a bright future for this format of data storage. It does not look as though it may die out with the LP and cassette, especially with crystal quality sound, more advance 'readers' and 'players', home recordable CD's and DVD's it looks as though there's no stopping this 12 centimetres of plastic. But with MP3 and Mini discs on the horizon, the CD may not be able to do as much for us as we thought. About the CD James T Russell gave birth to the concept of information reproduced without physical contact in the late 1960's. After many years of experimenting the first compact discs were tested successfully in the late 1970's. However they were not very similar in appearance to the CD's we are familiar with today. ...read more.


When they interfere on the returning journeys the two rays in effect cancel each other out, as there path difference will be precisely half a wavelength. In the same way waves can emphasize each other, as well as cancel each other out. In the diagram to the right you will see that in the second circumstance at the bottom, the waves return 'in-step' or 'in phase' with each other, (i.e. no path difference) combining to make a larger amplitude wave, with the same wavelength that is reflected. The first situation is what is known as destructive interference, and the lower is called constructive interference. In the system this constructive interference will occur when they two rays reflect off of the same surface level, either a bump or 'land'. Thus creating the perfect means for identifying between the two heights. There for, the basis for reading the disc all lies in light intensity. As I said this all relies on the height of the bump on the disc, which is one quarter of the wavelength of the laser. However, the laser passes through the polycarbonate plastic before it meets the information layer of pits, during which distance the wavelength will alter, as it will be slowed down due to the change in medium. To find out the new wavelength of the laser beam we must know the refractive index of the plastic. This can be done by using Snel's law. As you can see from the diagram on the left the angle of incidence (i) is 27� and the resultant angle is 17�. Snel's law states that (refractive index) ? = sin(i) / sin(r) ...read more.


Hardware Installations ? Computer Console Gaming This vast usage of the CD can be based on its production costs. Compared to a book the cost per 'bit' of information is considerably cheaper. Also, the CD's size is another reason for its success. Whole libraries can be dramatically reduced in size, if their books are replaced with compact discs as the average book contains in computer terms 3kbytes of data per page compared to the CD's 750Mbytes of information space. That's equivalent to approximately 250'000 book pages! However the CD is still being improved upon. DVD's (Digital Video/Versatile Discs) with are the same size as CD's are being transformed to contain up to nine hours of impeccable quality visual and audio information, by enhancing by MPEG2 format. CD's have also been squashed down into the latest in personal music technology called the minidisc. As it less than half the size of a standard CD, yet with the same capacity it is more fragile and is encased in another layer of plastic that makes it similar in appearance to the 31/2inch floppy disc. The minidisc has the advantage of the incredible ease of recording and re-recording music from other music sources and CD's, plus the benefit of even more compact size. It seems the CD has given birth to a wide range of inventions that seize the advantage of non contact reading, that means the products are much more durable. The CD has become one of the most inspiring and productive pieces of modern technology that we have ever known and it will continue to evolve and grow in our world filled with information. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Computer Science section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Computer Science essays

  1. Computing Project

    unit Ulogin; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, DB, ADODB; type TFMLogin = class(TForm) EdUserName: TEdit; EdPass: TEdit; Label1: TLabel; Label2: TLabel; Label3: TLabel; Btnlogin: TButton; ADOuandpsetup: TADOTable; DSuandpsetup: TDataSource; procedure BtnLoginClick(Sender: TObject); private { Private declarations } public { Public declarations } end;

  2. James. T. Russell and the Invention of the Compact Disc.

    He was familiar with digital data recording, in punch card or magnetic tape form. He knew that if you could represent the binary 0 and 1 with dark and light, then a device could be produced that is able to read sounds or any other information without wearing it out

  1. With diagrams compare and contrast the relative advantages and disadvantages of digital transmission over ...

    total number of data bits is even, the parity bit is set to one so that the total number of bits transmitted will form an odd number. If the total number of data bits is already an odd number, the parity bit remains or is set to 0.

  2. Computing Project

    14/03/2008 13:00:00 31321694 189 Alwark way, Nottingham, NT895TT Stephanie Jacob 20/03/2008 14:15:00 32668736 3A Leicester road, Nottingham,NT65JS Alex Wright 20/03/2008 16:45:00 35694784 78 Ratcliffe Road, Newcastle, NW156AS Neil Lawrence 21/03/2008 10:30:00 52854725 25 Ashby Square,Dundee, DN124AA Khris Johnson 20/03/2008 10:30:00 54587952 22 Aspire Street, Newcastle, NW1236GH Robert Taylor 14/03/2008 08:00:00

  1. Smart Card System

    The following process describes the lock-and-key access operation: 1. A user opens a Telnet session to a border (firewall) router configured for lock-and-key. The user connects via the virtual terminal port on the router. 2. The Cisco IOS software receives the Telnet packet, opens a Telnet session, prompts for a password, and performs a user authentication process.

  2. CP3 - Proposed Solution to a Realistic Problem - Apartment Administration software

    ( The use of software is ineffective, inappropriate and minimal. ( 0 No implementation is present or is of an inappropriate standard. ( Chapter 6 - Program Documentation (a) produce appropriate program and user documentation (This should cover the developed module(s) only. The prototype should be tested and evidence provided.)

  1. Statistics - How good are people's memory considering different factors?

    Also written on that sheet will be the age and gender of the person. The Need for the Data Now when I have gotten all the information that I need, I must use it accordingly to achieve all three of my hypotheses. This would mean to divide the data accordingly.

  2. Definition-nature of the problem solved - Car Mechanic business

    Instead a word processor must be incorporated for a proper receipt to be produced. Design Nature of the Solution 5.1.1 Objectives Input Objectives Customers personal data must have secure access through a login and password The database must be easy to use for a novice user.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work