Compact Disks
1 If someone says to you your music CDs don’t really hold any music on them, and they only have numbers recorded on them, you may not believe it. In fact, he is right in that sound is actually recorded onto the CDs as special numbers — a digital code.1 The code is pressed onto the CD as bumps on a long spiral track almost five kilometerslong. These bumps are an average of 0.5 microns wide.
2 A small laser beam shines onto the bumps as the CD turns. The light is reflected back to a receiver that records how the laser light bounces back. This lets the CD player2 turn the reflected light back into the original code. This means you can hear the original code as music.
3 Digital codes are used with many technologies. E-mail needs these kinds of code numbers. Space probes communicate with their ground station on earth using digital codes. Bar codes are read as digital codes in computer systems. Digital communications with cell phones need digital codes. Weather radios also tune in to specific signals using these codes.
4 There are many types of compact disk. One format is called CD-RWs. They can be recorded on and re-recorded on (rewritten on) as you would do with a floppy disk3. Another format is the CD-ROM. The technology for recording on these disks is different from other CDs. These CDs have a dye layer that the CD writer can darken or leave clear. The clear and dark spots are the digital code. CD-ROM stands for Compact Disc — Read Only
Memory.4 This disk is like a “super” floppy disk that can hold lots of information. One CD-ROM can hold the same amount of data as 500 floppy disks. Information is permanently recorded onto it. Computer games and other programs are considered to be CD-ROMs.
5 CDs were first sold to the public in 1982. These CDs still play well and sound fine. Current CDs are expectedto last between 70 to 200 years. Of course, you can make sure your CDs last a long time by taking care of them.
6 Science keeps on developing. It may not be many more years before a completely new technology is invented5 and introduced to the public for music recording. In the meantime, there is no doubt you will continue to enjoy listening to your favorite music on CDs6 and playing your favorite computer games on CD-ROMs.
練習:
graphs 1 & 2__________
2. Paragraph 3__________
graph 4__________
graph 5__________
A Digital Code Has Wide Applications
B Floppy Disks Are Outdated
C CDs Are Durable
D CD’s Working Principle Is Explained
E CD-RWs Play Better Than CD-ROWs
F CDs Are of Many Formats
5. One advantage of CD-RWs is that they can like floppy disks.
6. The author predicts it will not before a new technology is invented for music recording.
7. The laser beam-emitting device and the receiver are considered to of a CD player.
8. Space probes could not without using digital codes.
A shine on bumps
B take many more years
C be the key parts
D restore the original code
E be written on and rewritten on
F keep contact with their ground station efficiently
答案與題解 :
1. D第一、二段介紹了 CD的工作原理。聲音以數碼的形式刻錄到 CD磁片上。要想聽聲音，就得用 CD放機，CD機用鐳射照射 CD，接收機接收和分析從 CD反射回來的鐳射波，還原為原來的數碼，再轉換為原來的聲音。所以， D是答案。
2. A 第三段第一句“ Digital codes are used with many technologies.”是主題句。本段其他句子提供例證，即應用領域。作者列舉了 5個領域：電郵、航天通訊、條碼、手機和天氣預報。選項 A的“Digital code has wide applications”與主題句的意思完全吻合，所以是答案。
3. F 第四段第一句：“ There are many types of compact disks.”是主題句。本段其他句子列舉了兩種常用的 CD格式(format)：一種是 CD-RW，另一種是 CD-ROM。選項 F的“CDs are of many formats”概括了本段的大意，是答案。
4.C 第五段說的是 CD碟片經久耐用， 1982年上市的 CD碟片至今還能使用，其音質依舊。現在上市的. CD，更加耐用，如果使用得當，其壽命可達 70～200年。選項 C用了 durable予以概括是很恰當的，所以， C是答案。 5. E 第四段中出現 CD-RW這個詞，介紹了“ They can be recorded on and re-recorded on (rewritten on)。這就是選 E的依據。
6. B第六段能找到與答案有關的句子，但 It may not be many more years before a completely new technology is invented and introduced to the public for music recording.
7. C 第二段說到在 CD機上還原數碼時依靠的是鐳射發射裝置和按收器。由此我們可以推論出鐳射發射器和接收器是 CD機的主要部件。所以 C是答案。
8. F 第三段第三句“ Space probes communicate with their ground station on earth using digital codes.”是選 F的依據。
