首页
登录
职称英语
Under proper conditions, sound waves will be reflected from a hillside or ot
Under proper conditions, sound waves will be reflected from a hillside or ot
游客
2024-02-14
56
管理
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 I1 the British used a practical application of this principle to detect German planes on their way to bomb London 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 be lying in wait at the right time and never to be surprised (袭击). 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 distance to send them ( their range of flight, in other words), the device was called radio directing and ranging, and from the initials the word radar was coined. [br] Radar enabled the English ______.
选项
A、detect German planes on their way to London
B、direct the outnumbered RAF planes effectively
C、confuse German bomber pilots
D、both A and B
答案
A
解析
从文章第二段第一句我们知道,在二战期间,英国人运用这一原理来探测敌人接近目标之前到伦敦的距离,这里所说的实际运用这一原理就是指雷达,所以正确答案为A;B.有效地指挥数量上占优越的皇家飞机,这也不对的,雷达可以探测敌机距离,但是人运用它来指挥飞机;C.迷惑德国轰炸机飞行员,这也不对,雷达没有这个功能;D.把A和B两项放在一起不符原文。
转载请注明原文地址:https://tihaiku.com/zcyy/3449761.html
相关试题推荐
Treesarearenewableresourcethatwhenmanagedproperlycan______ourneedsin
【B1】[br]【B11】A、downtownB、suburbsC、properD、districtsB根据后面同位语判断。后文也提示,20世纪50
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Underproperconditions,soundwaveswillbereflectedfromahillsideorot
Underproperconditions,soundwaveswillbereflectedfromahillsideorot
随机试题
[originaltext]M:Ididn’tseeyouincreativewritingclasstoday.Whathappene
Forthelastfiftyyears,theglobehasbeenwarmingup.Itistruethat
河外星系都在远离我们而去,并不意味着我们处于“宇宙的中心”。造成无数星系四散离去
某企业生产中需要的检验员同产量有着密切的关系,经验表明,每个检验员每月可检验12
“贾人(商人)夏则资(购买)皮,冬则资絺(夏天用的细麻布),旱则资舟,水则资车”
商洛花鼓是一种在“跳”和“舞”中()的民间艺术。A.歌唱 B.说唱
A.奥美拉唑 B.盐酸赛庚啶 C.盐酸苯海拉明 D.盐酸雷尼替丁 E.马
根据《城市工程管线综合规划规范》,位置受限时,工程管线干线综合管沟应敷设在(
参与全国银行间债券回购业务的金融机构应在()开立债券托管账户。 A.中央结算
在心理诊断过程中使用的心理测理工具,应具有( )的特点。A.针对性 B.
最新回复
(
0
)