国产av不卡一区二区_欧美xxxx做受欧美_成年人看的毛片_亚洲第一天堂在线观看_亚洲午夜精品久久久中文影院av_8x8ⅹ国产精品一区二区二区_久久精品国产sm调教网站演员_亚洲av综合色区无码一二三区_成人免费激情视频_国产九九九视频

 
 
 

The history of the laser

2013-02-06 10:42

 

Get Flash Player

Download

Welcome to EXPLORATIONS in VOA Special English. I’m Mario Ritter. This week, we tell about one of the most recognizable objects in science fiction — the laser. It is one of the best examples of how technology can go from the science of the future to everyday use in a short period of time. Faith Lapidus and Steve Ember tell us about the history and many uses for the laser.

Laser is short for Light Amplification by Stimulated Emission of Radiation. The idea behind lasers is complex. Just how complex? Consider that it took the mind of Albert Einstein to discover the physics behind the laser.

Theodore Maiman succeed in building the first working laser in nineteen sixty. Mr. Maiman worked at Hughes Research Laboratories in Malibu, California.

A laser fires a light beam. Before the laser, scientists developed a similar device: a maser which stands for Microwave Amplification by Stimulated Emission of Radiation. A maser is basically a microwave version of the laser. Microwaves are a form of electromagnetic radiation similar to, but shorter than, radio waves. The best-known use of masers is in highly accurate clocks.

In the nineteen fifties, researchers in the United States and Russia independently developed the technology that made both masers and lasers possible. Charles Townes was a professor at the Massachusetts Institute of Technology in Cambridge, Massachusetts. He and his students developed the first maser.

Russians Nicolay Basov and Aleksandr Prokhorov did their research in Moscow. Their work led to technology important to lasers and masers. The three men received the Nobel Prize in Physics in nineteen sixty-four.

The idea of a thin beam of light with deadly power came much earlier. By the end of the eighteen hundreds, the industrial revolution had shown that science could invent machines with almost magical powers. And some writers of the time were the first to imagine something like a laser.

In eighteen ninety-eighty, H.G. Wells published a science fiction novel called “The War of the Worlds.” In it, he described creatures from the planet Mars that had technology far beyond anything on Earth. Among their weapons was what Wells called a “heat ray.” Listen to actor Orson Welles describe the weapon in a famous radio broadcast of “The War of the Worlds” from nineteen thirty-eight.

“I shall refer to the mysterious weapon as a heat ray… It's my guess that in some way they are able to generate an intense heat in a chamber of practically absolute non-conductivity. This intense heat they project in a parallel beam against any object they choose, by means of a polished parabolic mirror of unknown composition, much as the mirror of a lighthouse projects a beam of light. That -- That is my conjecture of the origin of the heat ray.”

H.G. Wells’ description is not too far from the truth. All lasers have several things in common. They have a material that supplies electrons and a power source that lifts the energy level of those electrons. And, as Wells guessed, many lasers have mirrors that direct light.

Laser light is different from daylight or electric lights. It has one wavelength or color. Laser light is also highly organized. Light behaves like a wave and laser light launches in one orderly wave at a time from its source.

You are listening to the VOA Special English program EXPLORATIONS.

The physics of the laser may be complex. Still, it is just a story of how electrons interact with light. When a light particle, or photon, hits an electron, the electron jumps to a higher energy state. If another photon strikes one of these high-energy electrons, the electron releases two photons that travel together at the same wavelength. When this process is repeated enough, lots of organized, or coherent, photons are produced.

In Theodore Maiman’s first laser, a rod of man-made ruby supplied the electrons. A more powerful version of the flash on a common camera was used to lift the energy state of the electrons. Mirrors on either end of the ruby rod reflected and increased the light. And an opening at one end of the rod let the laser light shoot out — just like the flash ray of science fiction hero Buck Rogers.

Industry put lasers to work almost immediately after they were invented in nineteen sixty. But weapons were not first on the list.

The first medical operation using a laser took place the year following its invention. Doctors Charles Campbell and Charles Koester used a laser to remove a tumor from a patient’s eye at Columbia-Presbyterian Hospital in New York City. Since then, doctors have used lasers to cut and remove tissue safely with little risk of infections.

Other health uses include medical imaging and vision correction surgery. Eye surgeons use lasers in LASIK operations to reshape the cornea, which covers the lens of the eye. The reshaped cornea corrects the patient’s bad eyesight so he or she does not have to wear glasses or other corrective lenses.

Lasers have made measurement an exact science. Astronomers have used lasers to measure the moon’s distance from Earth to within a few centimeters. Mappers and builders use laser technology every day. For example, drawing a perfectly level straight line on a construction site is easy using a laser.

Energy researchers are using lasers in an attempt to develop fusion, the same energy process that powers the sun. Scientists hope fusion can supply almost limitless amounts of clean energy in the future.

Lasers have also changed the way we communicate. It is likely that laser light on a fiber optic network carried this EXPLORATIONS program at least part of the way to you if you are reading or listening online. Super-fast Internet connections let people watch movies and send huge amounts of information at the speed of light.

Manufacturers have used lasers for years to cut and join metal parts. And the jewelry industry uses lasers to write on the surface of the world’s hardest substance, diamonds.

Since nineteen seventy-four, the public has had direct experience with lasers — at the grocery store checkout line.

Laser barcode scanners have changed how stores record almost everything. They help businesses keep track of products. They help in storage and every detail of the supply process.

Experts say no company has put barcode technology to better use than Wal-Mart, based in Bentonville, Arkansas. By nineteen eighty-eight, all Wal-Mart stores used laser bar code scanners. Highly detailed records on its products, and how they were selling, helped Wal-Mart keep costs down. Today, Wal-Mart is the world’s biggest corporation.

Lasers are found in many products used almost everywhere. Laser printers can print out forms and documents quickly and are relatively low in cost. They are required equipment for offices around the world.

If you have a CD or DVD player, you own a laser. Laser disc players use lasers to accurately read or write marks on a reflective, coated plastic disc. A device turns these optical signals into digital information that becomes music, computer software or a full-length movie.

Over one hundred years ago, writers imagined that beams of light could be powerful weapons. Today, lasers guide missiles and bombs.

For example, pilots can mark a target invisibly with a laser. Bombs or missiles then track the target with deadly results.

And, yes, American defense companies are working on giant laser guns recognizable to science fiction fans everywhere. But there are technological difficulties. Scientific American magazine says huge lasers turn only about twenty to thirty percent of the energy they use into a laser beam. The rest is lost as heat.

That has not stopped scientists from working to perfect powerful lasers that, one day, may be able to shoot missiles out of the sky.

相關閱讀

Mobile telephones changing lives in Africa

American expressions based on colors

Americans making final preparations for Super Bowl Sunday

Words and their stories: food expressions, part II

(來源:VOA 編輯:Julie)

 
中國日報網英語點津版權說明:凡注明來源為“中國日報網英語點津:XXX(署名)”的原創作品,除與中國日報網簽署英語點津內容授權協議的網站外,其他任何網站或單位未經允許不得非法盜鏈、轉載和使用,違者必究。如需使用,請與010-84883561聯系;凡本網注明“來源:XXX(非英語點津)”的作品,均轉載自其它媒體,目的在于傳播更多信息,其他媒體如需轉載,請與稿件來源方聯系,如產生任何問題與本網無關;本網所發布的歌曲、電影片段,版權歸原作者所有,僅供學習與研究,如果侵權,請提供版權證明,以便盡快刪除。

中國日報網雙語新聞

掃描左側二維碼

添加Chinadaily_Mobile
你想看的我們這兒都有!

中國日報雙語手機報

點擊左側圖標查看訂閱方式

中國首份雙語手機報
學英語看資訊一個都不能少!

關注和訂閱

本文相關閱讀
人氣排行
搜熱詞
 
 
精華欄目
 

閱讀

詞匯

視聽

翻譯

口語

合作

 

關于我們 | 聯系方式 | 招聘信息

Copyright by chinadaily.com.cn. All rights reserved. None of this material may be used for any commercial or public use. Reproduction in whole or in part without permission is prohibited. 版權聲明:本網站所刊登的中國日報網英語點津內容,版權屬中國日報網所有,未經協議授權,禁止下載使用。 歡迎愿意與本網站合作的單位或個人與我們聯系。

電話:8610-84883645

傳真:8610-84883500

Email: languagetips@chinadaily.com.cn

中文在线一区二区| 精品一区二区三区高清免费不卡| 亚洲人高潮女人毛茸茸| 亚洲а∨天堂久久精品9966| 欧美日韩激情在线| 欧亚一区二区三区| 色综合久久久网| 亚洲国产综合在线| 亚洲精品成a人| 亚洲色欲色欲www| 国产精品视频yy9299一区| 91网在线观看| 先锋资源中文字幕| 91av在线国产| 午夜精品一区二区三区av| 欧美高清自拍一区| 欧美成人h版在线观看| 精品国产一区二区三区久久久| 国产亚洲精品美女| 一本大道亚洲视频| 在线播放国产精品| 色噜噜久久综合伊人一本| 中文字幕亚洲欧美一区二区三区 | 六月丁香婷婷久久| 蜜桃久久久久久| 美女精品自拍一二三四| 麻豆免费精品视频| 蜜桃一区二区三区四区| 久久99精品久久只有精品| 麻豆国产欧美日韩综合精品二区| 日韩在线一二三区| 免费成人在线影院| 国产在线看一区| 国产成人免费视频网站高清观看视频| 国产精品一二二区| 成人免费高清在线观看| 久久综合狠狠综合久久激情| 久久久精品国产免费观看同学| 欧美国产日韩亚洲一区| 亚洲欧美自拍偷拍| 亚洲一区二区精品3399| 欧美性猛交xxx| 欧美探花视频资源| 日韩一区二区三区视频在线| 精品国产乱码久久久久久久| 亚洲精品999| 国产亚洲欧洲在线| 久久成人一区二区| 亚洲v片在线观看 | 日韩视频不卡| 视频一区视频二区中文| 精品一区二区三区在线观看国产| 国产成人无遮挡在线视频| aaa亚洲精品一二三区| 久久九九久久九九| 一区二区三区免费观看| 欧美日韩中文字幕在线| 91.com在线观看| 亚洲激情免费观看| 最近2019年好看中文字幕视频| 欧美国产日韩在线| 亚洲综合爱爱久久网| 色版视频在线观看| 国产福利a级| 免费在线稳定资源站| a免费在线观看| 26uuu亚洲电影| 日韩精品视频一区二区三区| 自拍偷拍精品| 欧美日韩国产亚洲一区| 轻轻草成人在线| 91在线视频在线| 亚洲免费毛片网站| 欧美午夜免费电影| 亚洲精品福利资源站| 久久久精品亚洲| 一区二区三区小视频| 在线观看免费电影| 一本免费视频| 成人免费视屏| 高清在线一区| 国产精品亚洲人成在99www| 综合一区在线| 精品一区二区三区欧美| 久久久久久久av麻豆果冻| 亚洲第一福利一区| 日韩一区二区电影在线| 在线观看欧美日韩| 欧美亚洲国产另类| 成年网站在线在免费播放| 伊人75在线| 国产美女一区视频| 国产三级一区| 精品日本12videosex| 国产日韩一区| 暴力调教一区二区三区| 夜夜亚洲天天久久| 日韩一区二区免费在线电影| 精品国偷自产在线视频99| 四虎a级欧美在线观看| 久草在线免费二| 免费看a在线观看| 国产资源一区| 久久福利影院| 美女一区二区三区在线观看| 国产视频不卡一区| 91福利国产精品| 亚洲图片欧美午夜| 自拍偷拍国产| 成人高清免费| av免费网站在线观看| 激情不卡一区二区三区视频在线| 99精品小视频| 国产精品乡下勾搭老头1| 亚洲手机成人高清视频| 日韩一级片在线播放| 麻豆一区二区在线观看| 伊人免费视频| 男女视频在线观看免费| 中文另类视频| 91高清一区| 国产91高潮流白浆在线麻豆| 亚洲高清免费在线| 亚洲免费一在线| 亚洲欧美精选| 日本24小时在线高清视频| 亚洲色图官网| 日产精品一区二区| 国产精品一区二区在线播放 | 欧美中文字幕| 国产精品青草久久| 欧美一区2区视频在线观看| 久久久久五月天| 羞羞的视频免费| 第四色日韩影片| 免费成人av| 精品制服美女久久| 午夜久久久久久电影| 亚洲人午夜精品| 国产三级做爰在线观看| 国产原创av在线| 99久久这里有精品| 伊人精品成人久久综合软件| 99久久精品国产一区| 在线视频观看一区| 久久久久www| 女同性互吃奶乳免费视频| 亚洲成av人影片在线观看| 成人做爰视频www| 欧美人与拘性视交免费看| 毛片一区二区三区| 亚洲一区二区三区影院| 国产一区二区成人| 鲁啊鲁视频在线精品| 在线视频您懂的| 78精品国产综合久久香蕉| 欧美国产一区二区三区激情无套| 欧美bbbbb| 午夜精品久久久久影视| 亚洲国产三级网| 国产91精品久久久| 亚欧精品一区| 国产成人福利夜色影视| 午夜精品电影| 久久蜜桃av一区二区天堂| 欧美剧情片在线观看| 国内精品久久影院| 动漫成人在线| 电影亚洲一区| 影音先锋亚洲电影| 欧美激情在线一区二区三区| 日韩久久久精品| 男女猛烈无遮挡| 中文字幕高清在线观看| 99riav视频一区二区| 好吊一区二区三区| 国产精品国模大尺度视频| 涩涩视频在线播放| 日韩精品一区二区三区免费观影| 粉嫩aⅴ一区二区三区四区五区| 91国偷自产一区二区三区观看| 欧美成人午夜视频| caoporn超碰国产公开| 国产精欧美一区二区三区蓝颜男同| 一级欧洲+日本+国产| 久久久综合视频| 日韩精品一区二区三区蜜臀 | 久久精品亚洲精品国产欧美kt∨| 欧美一级黄色大片| 中文字幕国产欧美| 都市激情在线视频| 亚洲自拍都市欧美小说| 国产.精品.日韩.另类.中文.在线.播放 | 久久av影院| 亚洲欧美日韩国产| 亚洲午夜在线视频| 久久精品小视频| 日本福利小视频| 亚洲最新无码中文字幕久久| 国产视频久久| 亚洲高清免费视频| 欧美激情第1页| 超碰在线免费| 456亚洲精品成人影院| 美女久久一区| 婷婷激情综合网| 久久久之久亚州精品露出| 在线播放av片| 欧美不卡一区二区三区四区| 女生裸体免费视频| 蜜桃av在线| 在线成人h网| 亚洲无线码一区二区三区| 色香阁99久久精品久久久| 天堂影视av| 日韩激情综合| 国产99精品在线观看| 日韩欧美国产综合一区| 韩国av一区二区三区| 欧美美女一区二区在线观看| 一本一本久久a久久综合精品蜜桃 一道精品视频一区二区三区男同 一道精品视频一区二区三区图片 一二三四在线观看视频韩国 | 日韩欧美精品三级| 午夜娱乐在线| 国产精品av一区二区三区| 欧美一级二区| 色94色欧美sute亚洲线路一久| 亚洲色图偷窥| 久草免费在线观看| 亚洲素人在线| 国产欧美一区二区精品性色超碰| 精品夜色国产国偷在线| 天天躁日日躁狠狠躁超碰2020| 国产极品一区| 黄色精品一二区| 欧美在线观看视频一区二区三区| 国产麻豆一区二区三区精品| 91福利区在线观看| 性欧美精品高清| 欧美影片第一页| 555www成人网| 国产黄色大片在线观看| 99视频精品| 一本一道久久a久久精品| 91精品国产91久久久久久| 最新日本在线观看| 亚洲少妇自拍| 欧美日韩国产精品| 日韩在线天堂| 精品国产免费人成网站| 青青草伊人久久| 日韩一级欧美一级| 国产视频一二三区| 米奇精品关键词| 中文在线免费一区三区高中清不卡| 久久精品国产2020观看福利| yw193.com尤物在线| 亚洲综合婷婷| 精品久久久香蕉免费精品视频| 自拍偷拍国产| 毛片无码国产| 波多野结衣中文字幕一区二区三区| 亚洲美女www午夜| 亚洲а∨精品天堂在线| 日本欧美肥老太交大片| 午夜av一区二区| 亚洲国产一区二区久久久777 | 2020国产精品视频| 蜜臀av国内免费精品久久久夜夜| 午夜一区二区三区不卡视频| 欧美精品色一区二区三区| 欧美日韩中文字幕一区| 欧美高清dvd| 女同性互吃奶乳免费视频| 成人亚洲精品| 成人免费毛片a| 中文字幕日韩精品在线观看| 日本成人一区| 欧美日韩hd| 好吊成人免视频| 青青草免费观看完整版高清| 欧美午夜在线播放| 中文子幕无线码一区tr| 2019中文字幕在线观看| 亚洲成人人体| 不卡一区二区三区四区| 久久手机精品视频| 久cao在线| 久久精品99国产精品日本| 国产视频亚洲视频| 黄色av免费在线看| 日韩视频免费| 亚洲精品一区二区三区香蕉| 高清欧美精品xxxxx在线看| 天天做天天爱天天综合网| 欧美性xxxx在线播放| 夜色资源网av在先锋网站观看| 奇米777国产一区国产二区| 亚洲综合无码一区二区| 精品极品三级久久久久| 亚洲男女网站| 国产精品久久久久7777按摩| 最新版天堂中文在线官网| 国产精品毛片久久久久久久久久99999999| 国产精品自在在线| 久久久国产精品视频| 午夜影院免费在线| 久久se精品一区二区| 精品偷拍各种wc美女嘘嘘| www.中文字幕久久久| 久久综合九色综合欧美狠狠| 日韩精品免费在线观看| 伊人75在线| 天使萌一区二区三区免费观看| 日韩激情片免费| 香蕉视频在线播放| 狠狠色丁香婷婷综合| xxx成人少妇69| 福利成人导航| 成人午夜电影网站| 亚洲第一色网| 日韩av黄色| 中文字幕亚洲在| 国产青草视频在线观看视频| 91国产美女视频| 不卡av影片| 国产视频一区二区在线| 男人扒开美女尿口无遮挡图片| 久久91视频| 亚洲欧美一区二区不卡| 午夜视频免费播放| 精品99久久| 色哟哟国产精品| 在线播放国产区| 欧美在线亚洲| 日韩精品中文字幕有码专区| 黄色网址在线免费播放| 国产精品主播直播| 欧美亚洲在线观看| 精品91福利视频| 亚洲一区二区三区四区在线免费观看| 国产欧美在线观看视频| 欧美一区二区三| 777xxx欧美| 黄色小视频在线观看| 国产大陆精品国产| 成人网6969conwww| 日韩精品久久久久久久软件91| 亚洲午夜精品久久久久久久久| 成年网站免费| 国产午夜精品一区二区三区欧美| 亚洲天堂av网| 日韩三级免费| 久久久久久9999| 国产1卡2卡三卡四卡网站| 国内精品久久久久久久影视简单 | 性欧美高清强烈性视频| 秋霞影院一区二区三区| 欧美日韩一级视频| 国产午夜精品一区理论片| 国产91精品一区二区麻豆网站| 私人影视中文字幕| 激情亚洲另类图片区小说区| 亚洲成a人片在线观看中文| 男人天堂免费视频| 日韩专区欧美专区| 美乳少妇欧美精品| 精品一区二区三区中文字幕| 天天爽夜夜爽夜夜爽精品视频| 国产美女被遭强高潮免费网站| 精品白丝av| 不卡av日日日| 成人免费91| 在线看日韩精品电影| 国产系列在线观看| 粉嫩欧美一区二区三区高清影视| 蝴蝶中文综合娱乐网| 午夜精品福利影院| 日韩亚洲欧美高清| 中文字幕伦理免费在线视频| 成人小视频在线观看| 99久久国产视频| 我不卡神马影院| 亚洲欧美国产精品久久久久久久 | 成人午夜影院| 久久精品在线| 久久琪琪电影院| 婷婷成人综合| 欧美v日韩v国产v| 国产精品69xx| 亚洲电影一级黄| 色在线免费视频| 丁香婷婷深情五月亚洲| 色九视频91| 欧美日韩精选| xxxxx成人.com| 精品国产影院| 精品国产一二三| 天堂电影一区| 一本久道久久综合中文字幕| 成年人视频在线免费观看|