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
专升本
Under proper conditions, sound waves will be reflected from a hillside or other such obstruction. Sound travels at the rate of a
Under proper conditions, sound waves will be reflected from a hillside or other such obstruction. Sound travels at the rate of a
admin
2010-10-31
46
问题
Under proper conditions, sound waves will be reflected from a hillside or other such obstruction. Sound travels at the rate of about one-fifth of a mile per second. If the hill is eleven hundred feet away, it takes two seconds for the sound to travel to the hill and back. Thus, by timing the interval between a sound and its reflection (the echo) , you can estimate the distance to an obstruction.
During World War II the British used a practical application of this principle to detect German planes on their way to bomb London long before the enemy was near the target.
They used radio waves instead of sound waves, since radio waves can penetrate fog and clouds.
The outnumbered Royal Air Force(RAF) always seemed to the puzzled Germans to by lying in wait at the right time and never to be surprised. It was radio echoes more than anything else that won the Battle of Britain.
Since the radio waves were used to tell the direction in which to send the RAF planes and the distance to send them (their rage of flight, in other words) , the device was called "radio directing and ranging" , and from the initials the word "radar" was coined.
Practical application of this principle resulted in______.
选项
A、new electronic instruments for planes
B、a radio directing and ranging device
C、new radio sets for RAF bombers
D、an electronic detecting device
答案
B
解析
第二段的大意是:二战的时候,英国人将这个原理应用于实战,只是他们使用的是无线电波,而不是声波,因为无线电波能穿透雾气和云层。第三段继续就无线电波展开,并且说明“雷达”这个词的由来。因此答案为B(无线电探测器,雷达)。
转载请注明原文地址:https://jikaoti.com/ti/S2JGFFFM
本试题收录于:
英语题库普高专升本分类
0
英语
普高专升本
相关试题推荐
Since1950s,thecomputerindustryhas______.Althoughcomputersareusedinalmosteveryaspectsofbusiness,theycan’trepl
He______thathisguestswerebored,althoughtheywerelisteningpolitely.
______isnotknownwhattheydiscussedinthemeeting.
Teachersaresupposedtobepatientandnottolosetheirtempernomatterwhatmistakestheirstudentsmake.
Wedidn’tknowhistelephonenumber,otherwisewe______him.
Therearemanyproblemsinourmodernworld.Oneveryseriousproblemisenergy.Wegetagreat【71】ofenergyweneedfromcoal
Itisafactthatthiscountry’susingupenergyfasterthanweproduceit.
Itisestimatedthatabout80%oftheworld’spopulationcannotaffordtohaveproperfood,housingormedicalcare.
______canbeproperlycalledaclockalwaysstrikesthehoursandtellsthetime.
随机试题
体温调定点的高低主要决定于
急性心肌梗死胸部疼痛宜用下列哪种药物镇痛
心跳骤停最主要的临床征象是
肝肾不足证闭经首选方是肝,肾不足证痛经首选方是
【给定资料】1.媒体披露H省一中学发生群发性肺结核事件后,A县政府官网于2017年11月16日中午通报证实确有此事,但对事件涉及的范围和人数只字未提。而根据《结核病防治管理办法》,肺结核疫情严重,构成突发公共卫生事件的,应当及时向社会公布疫情处置
韩亚航空的波音777客机在旧金山机场失事,造成3名中国少女遇难,此事引发了公众对航空安全的关注。统计数据显示,从20世纪50年代到现在,民用航班的事故率一直在下降,每亿客公里的死亡人数,1945年为2.78人,1950年为0.90人,近30年为0.013人
软件详细设计生产的图如下该图是()。
Globalizationisaphenomenonandarevolution.Itissweepingtheworldwithincreasingspeedandchangingthegloballandscape
______Iacceptthatheisnotperfect,Idoactuallyliketheperson.
WhichofthefollowingsentencesindicatesPOSSIBILITY?
最新回复
(
0
)