Not all long-distance phone calls are made over phone wires.Today,phone wires are being replaced by fiber optics.Fiber optics make telephoning faster and easier than ever before.
In the past,telephone calls were made mostly over copper wires.Copper wires are heavy and bulky.Fiber optics are flexible,glass fibers.They are no thicker than a human hair.A wire cable is as thick as a mans arm.An optical fiber cable is as thick as a thumb.
Fiber optics transfer sound into light.First,a person speaks into a phone.The sound is changed into electrical impulses.A small laser changes the electrical impulses into coded bursts of light.The light is decoded hack into electrical impulses at the telephone recieving station.Finally,the electrical impulses are changed into sounds again at the receiving telephone.
Optical fibers transimit calls much faster than copper wires can.The laser pulses with light as fast as 90 million times a second.At that speed,every word in a dictionary can be sent through a single fiber in a few seconds.Optical fibers also save space.A few fibers can carry more calls than thousands of strands of copper cable.
Optical fibers will be used for video as well as voice communications.And they will prove useful in computer-to-computer hookups.However,it will take years to replace existing wires.
1.Which of the following best expresses the main point of the passage?
a.Fiber optics are flexible,glass fibers.
b.Copper wires have been used in most phone systems.
c.Fiber optics are an improvement in communication systems.
d.A few optical fibers can carry thousands of phone calls.
2.As it is used in the passage,the phrase fiber optics means _____.
a.transmission of information by means of infra-red light signals aling a thin glass fiber.
b.material or substance formed from a mass of fibers.
c.a flexible fiber-optic instrument that is used to view objects
d.a composite material consisting of glass fibers in resin
3.Which of the following can not be inferred about fiber cables from the passage?
a.They carry light waves.
b.They can be used in many forms of communication.
c.They are better than copper wires.
d.They are shorter than copper wires.
4.You can infer from the passage that a cable is _____.
a.a group of wires or strands that are bundled together
b.a copper wire that is used to carry phone calls
c.a glass fiber that carrise coded bursts of light
d.a laser that changers electrical impulses into light
5.You can infer from the passage that the word transmit most nearly means _____.
a.carry from one place to another
b.pulse with light
c.operate quickly
d.speak
答案:cadaa
奥运会知识科普:奥运会会旗与圣火的含义
《功夫熊猫3》重返江湖背后的故事
双语美文:愿你知足常乐,尽享人生
双语美文:学着做个碱性人
幸福与悲伤的盒子,一个珍存一个释放
何种植自己的幸福?幸福培植技巧揭秘
幸福的误解:娱乐并不等于幸福
乒乓球辉夜球迷不得不知的大小事盘点
哥本哈根:一个比安迪生童话更令人着迷的地方
斯诺克知识科普:高标准的礼仪举止
朗朗:音乐天才的成功之路
奥运会开幕仪式知识科普:代表团出场顺序有讲究
拳王阿里眼中的自己:我依旧是“最伟大的”
盘点世界各地的奇特婚礼习俗
钓鱼爱好者的天堂:钓鱼者协会
网球运动;寺院和尚的发明?
梦想经不起等待,现在就可以开始起航
双语美文:今天,你戒掉抱怨了吗?
网球运动历史解密:网球运动的前世今生
人生就是一盘棋,投入就是幸福
国际奥委会知识科普:官方语言及中国官员简介
简单的幸福,柏拉图式的永恒
双语美文:自己的幸福自己负责
《疯狂动物城》:顺利打破迪士尼票房记录
奥林匹克会歌:一百年前的希腊圣歌
夏威夷印象:热情与生俱来
网球的专属语言,网球运动的入门语言
爱是幸福生活的关键
23岁、29岁,人生最快乐的两个年龄
关于色彩心理学的那些小事
| 不限 |
| 英语教案 |
| 英语课件 |
| 英语试题 |
| 不限 |
| 不限 |
| 上册 |
| 下册 |
| 不限 |