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
40
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.
Which of the following statements best describes a laser?
选项
A、A device for stimulating atoms and molecules to emit light.
B、An atom in a high-energy state.
C、A technique for destroying atoms or molecules.
D、An instrument for measuring light waves.
答案
A
解析
下列陈述最能描述激光:A刺激原子和分子发出光来的发明;B高能量状态下的原子;C破坏原子或分子的技术;D测定光波的器械。第一段中谈到:激光是辐射刺激性放射光扩大的首字母缩略词,而原子或分子被刺激而发射出来的光不同于自然发射的光。故A为正确选项。
转载请注明原文地址:https://kaotiyun.com/show/tr6K777K
0
专业英语四级
相关试题推荐
Deathpenaltyornot?Thatisaquestionfacingjudgeswhohandlechild-traffickingcasesthesedays.Lately,callsonsocialme
It’sacommonmisconceptionthatpovertyalleviationisallaboutfinancialaid.Peopleregardthisasthemosteffectivewayto
HowtoFightDepressionWithoutOutsideHelpDepressionisacommonfeeling,butsometimesitcanbecome【T1】______.【T1】____
HowtoFightDepressionWithoutOutsideHelpDepressionisacommonfeeling,butsometimesitcanbecome【T1】______.【T1】____
HowtoFightDepressionWithoutOutsideHelpDepressionisacommonfeeling,butsometimesitcanbecome【T1】______.【T1】____
Earlychildhoodisatimeoftremendousgrowthacrossallareasofdevelopment,especiallythelanguageskills.Frombirt
(1)Forsomeonewhoissuchanextraordinarilysuccessfulinvestor,WarrenBuffettcomesoffasaprettyordinaryguy.Bornandb
(1)There’sabriefsceneinthebackhalfofPixar’sUpinwhich8-year-oldRussellrecallshow,yearsbefore,hisestrangedfa
PassageOne(1)BeingtoldIwouldbeexpectedtotalkhere,IinquiredwhatsortoftalkIoughttomake.Theysaiditsho
Thereareseveralpossiblerelationshipsbetweenlanguageandsociety.Oneisthatsocialstructuremayeitherinfluenceordet
随机试题
气逆病变多见于下列哪些脏腑:
下列选项不属于牛蒡解肌汤与银翘散共同含有的药物是
下列不符合老年人用药原则的有
新生儿早发型败血症是指
A.佐助药B.佐制药C.使药D.君药E.臣药调和诸药作用,使其合力驱邪的是()
王平住在北京市海淀区,有儿子王大、王二和女儿王三。王平立一遗嘱交给其女王三。遗嘱中列明,其遗产房屋全部由王三继承。后来,王平死亡,死后丧葬费均由王大承担。王大为其父办完丧事后,便将其父遗留的房屋卖给李大。王二回来后,向法院提起诉讼,要求继承遗产。海淀区法院
业主是物业管理企业提供管理服务的对象,业主分为()几个层次。
招标人已收取投标保证金的,应当自收到投标人书面撤回通知之日起()日内退还。
根据我国外商投资企业法律制度的规定,境外投资者申请将原出资币种由外币变更为人民币时办理相关手续的表述中,正确的有()。
所有的聪明人都是近视眼,我近视得很厉害,所以我很聪明。以下哪项与上述推理的逻辑结构一致?
最新回复
(
0
)