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
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
2013-05-19
50
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.
The British used radio waves because they______.
选项
A、were more exact than sound waves
B、could not be detected
C、could penetrate fog and clouds
D、were easier to use than sound waves
答案
C
解析
从文章第二段第二句我们知道,他们(英国人)使用无线电波而不是声波是因为无线电波能够穿透云雾,所以正确答案为C;A.(无线电波)比声波更精确;B.不能被探测;D.比声波更容易使用;这三项显然不对。
转载请注明原文地址:https://kaotiyun.com/show/bkg7777K
0
大学英语四级
相关试题推荐
WhyDIY?ThereasonswhypeopleengageinDIYhavealwaysbeennumerousandcomplex.Forsome,DIYhasprovidedarareoppor
WhyDIY?ThereasonswhypeopleengageinDIYhavealwaysbeennumerousandcomplex.Forsome,DIYhasprovidedarareoppor
WhyDIY?ThereasonswhypeopleengageinDIYhavealwaysbeennumerousandcomplex.Forsome,DIYhasprovidedarareoppor
WhyDIY?ThereasonswhypeopleengageinDIYhavealwaysbeennumerousandcomplex.Forsome,DIYhasprovidedarareoppor
Japanisgettingtoughaboutrecycling—andnotinthepaperandplastickindofway.Recently,thecountryrequiresthatallele
Itseemsyoualwaysforget—yourreadingglasseswhenyouarerushingtowork,yourcoatwhenyouaregoingtothe【11】,yourcred
A、Ifheandhiswifeareinterestedinthebusinessofthecompany.B、Theconditionsofthecar.C、Thecouple’sdrivingexperien
A、Histravels.B、Hisshortstories.C、Hiswealth.D、Hisfamily.A主旨题。解答该题可用排除法,文章提到了马克·吐温的写作,但未具体到他的短篇故事,至于他的财富和家庭则更少提及。英语中的tra
Settingofffirecrackersisseennotmerelyasa(an)______lintalsoabigthreattoman’slifeandproperty.
随机试题
若某事件经过风险评估,位于事件风险量区域图中的风险区A,则应采取的措施是()。
在计算机中,指令和数据均是以二进制代码存放的,那么能够区分指令和数据的部件是()。
中国社会阶级状况决定了民主革命的主力军是【】
生化汤中重用当归为君的意义在于
A.葡萄柚汁B.咖啡C.食醋D.高蛋白E.脂肪服用灰黄霉素时,应多食
药品广告审查的依据是
人的感知电流是指电流通过人体时,引起人有发麻感觉及轻微针刺感的最小电流。就工频电流有效值而言,人的感知电流约为()mA。
人造防眩设施主要包括()。
在观察精确性上有明显提高的阶段是小学()年级。
学习是由经验引起的个体行为的相对持久的变化。()
最新回复
(
0
)