首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The word laser was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from th
The word laser was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from th
admin
2010-01-10
28
问题
The word laser was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation. Ordinary light, from the Sun or a light bulb, is emitted spontaneously, when atoms or molecules get rid of excess energy by them-selves, without any outside intervention. Stimulated emission is different because it occurs when an atom or molecule holding onto excess energy has been stimulated to emit it as light.
Albert Einstein was the first to suggest the existence of stimulated emission in a paper published in 1917. However, for many years physicists thought that atoms and molecules always were much more likely to emit light spontaneously and that stimulated emission thus always would be much weaker. It was not until after the Second World War that physicists began trying to make stimulated emission dominate. They sought ways by which one atom or molecule could stimulate many others to emit light, amplifying it to much higher powers.
The first to succeed was Charles H. Townes, then at Columbia University in New York. Instead of working with light, however, he worked with microwaves, which have a much longer wavelength, and built a device he called a "maser," for Microwave Amplification by the Stimulated Emission of Radiation. Although he thought of the key idea in 1951, the first maser was not completed until a couple of years later. Before long, many other physicists were building masers and trying to discover how to produce stimulated mission at even shorter wavelengths.
The key concepts emerged about 1957. Townes and Arthur Schawlow, then at Bell Telephone Laboratories, wrote a long paper outlining the conditions needed to amplify stimulated emission of visible light waves. At about the same time, similar ideas crystallized in the mind of Gordon Gould, then a 37-year-old graduate student at Columbia, who wrote them down in a series of notebooks. Townes and Schawlow published their ideas in a scientific journal, Physical Review Letters, but Gould filed a patent application. Three decades later, people still argue about who deserves the credit for the concept of the laser.
Why was Towne’s early work with stimulated emission done with microwaves?
选项
A、He was not concerned with light amplification.
B、It was easier to work with longer wavelengths.
C、His partner Schawlow had already begun work on the laser.
D、The laser had already been developed.
答案
B
解析
为什么汤尼斯早期的刺激性放射工作是用微波来进行的?A他对光的扩散不感兴趣;B和更长的波长一起使用更方便;C他的伙伴 Schawlow已经开始对激光的研究;D激光已经被开发。第三段第一,二句话表明:最初的成功人物是查尔斯H-汤尼斯,他在纽约的哥伦比亚大学(美)工作。没有用光来工作,他利用微波,因为它有更长的波长。他还建造叫做微波激射器的装置,为辐射刺激性放射的微波扩大。故应选B。
转载请注明原文地址:https://kaotiyun.com/show/3r6K777K
0
专业英语四级
相关试题推荐
Toauniversitystudentwhoisdoomedtoenterintosocietytorealizehimself,whichismoreimportant—educationorsociallif
Nowadays,manypeopleturntotheInternettosolveamultitudeofmedicalquandaries,extendingeventothemattersofhowtof
HowtoFightDepressionWithoutOutsideHelpDepressionisacommonfeeling,butsometimesitcanbecome【T1】______.【T1】____
WritingaResearchPaperI.ResearchPaperandOrdinaryEssayA.Similarityin【T1】________:
A、Sixpounds.B、Sevenpounds.C、Eightpounds.D、Ninepounds.B细节题。Jason提到了去吃早午餐,说brunch包含了早餐和午餐的东西:Youjustpaysevenpoundsper
PassageOne(1)BeingtoldIwouldbeexpectedtotalkhere,IinquiredwhatsortoftalkIoughttomake.Theysaiditsho
Thereareseveralpossiblerelationshipsbetweenlanguageandsociety.Oneisthatsocialstructuremayeitherinfluenceordet
Becauseoftheunexpectedchanges,theypostponed______usananswer.
Mac’sclose______tohisbrothermadepeoplemistakethemforoneanother.
________hedaydreamed,Petersawfiguresinthesky.
随机试题
材料1一天,家住乌石镇大塘村的黄老伯要去自家山坡上,经过院子时,被围鸭的篱笆挡住了去路,他急着赶路,抬脚迈过去,没想却被篱笆绊了一下,重重地摔倒在地上,老人动弹不得。村民王福恰巧路过,看到这个情况,急忙通知黄老伯的儿子把黄老伯背回了家。
子宫内膜异位症的临床表现不包括()
一位62岁男性患者,患慢性支气管炎伴肺气肿已10年。此次因主动脉瘤人院手术,手术中出血约1150ml,手术中输液1100ml,输红细胞悬液5单位。处置中以输液和红细胞为主,未输全血,其主要理由是
A、单体B、二聚体C、三聚体D、四聚体E、五聚体SIgA为
下列属于城乡居民储蓄存款余额的是( )。
封闭式基金的交易遵从( )的原则。
S公司新研发的产品由于其自身特性,加之公司的大力宣传,广受顾客青睐。该公司所在产业的产品市场增长率很高,虽然现在的相对市场占有率不是很大,但是未来发展的空间很大。根据波士顿矩阵理论,下列关于该产品的说法中正确的有()。
将f(x,y)dxdy化为累次积分,其中D为x2+y2≤2ax与x2+y2≤2ay的公共部分(a>0).
Forthispart,youareallowed30minutestowriteacompositiononthetopicontheIncreasingNumbersofTravelers.Youshould
旗袍(cheongsam)起源于满族妇女的民族服装,随着满汉生活的融合(integration),汉族妇女逐渐接纳了旗袍,并不断对其进行革新。旗袍的造型(shape)与妇女的体态相适合,线条简洁,优美大方。根据季节的变化和穿着者的不同需要、喜好,可长可短。
最新回复
(
0
)