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
39
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] Practical application of this principle resulted in ______.
选项
A、new electronic instruments for planes
B、new radio sets for RAF bombers
C、an electronic detecting device
D、a radio directing and ranging device
答案
D
解析
从文章的最后一段我们知道,因为使用电波告诉皇家空军飞行方向和飞机距离,所以这种装置就被称作无线电探测器,从它的首字母缩略就创造了radar(雷达)一词,所以正确答案为D;A.新的飞机电子装置;B新的皇家轰炸机无线电装置;C.电子探测器,这三个选项均不十分准确。
转载请注明原文地址:https://tihaiku.com/zcyy/3449760.html
相关试题推荐
Treesarearenewableresourcethatwhenmanagedproperlycan______ourneedsin
[audioFiles]audio_eufm_j58_001(20082)[/audioFiles]A、Sheshouldfindaproperjo
Iftheseclothesareproperlymerchandised,_____________(它们在圣诞节前应该相当好卖).theysh
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Studentshavebeencomplainingmoreandmoreaboutstolenproperty.Radios,
Lawsconcerningdiscriminationandtheconditionsunderwhichindividualsmaybe
Underproperconditions,soundwaveswillbereflectedfromahillsideorot
随机试题
[img]2014m3s/ct_etoeicrm_etoeicryd_0440_20136[/img][br]Theword"amendments"i
[originaltext]Aroundtheworldmoreandmorepeoplearetakingpartindang
Mrs.Brownissupposed______forItalylastweek.A、tohaveleftB、toleaveC、to
以下符合安全技术交底要求的有()。A.安全技术交底必须执行国家各项技术标准
已婚待孕女职工不应从事()A.体力劳动强度分级标准中第Ⅱ级劳动强度的作业
点着乙醇棉球快速在罐里绕一圈拿出,然后迅速拔在背上的方法是A.闪火法 B.投火
停电试验计划统一纳入检修计划,按照变电检修管理通用细则执行。
商业银行可以从()等的资产质量、收益维度对贷款组合进行结构分析,有效监测信用组合
下列哪项不属于细菌的代谢产物()A.热原质 B.毒素 C.维生素、色素 D
智能公交系统的核心部分是( )。A.车辆定位技术 B.图像监控系统 C.地理
最新回复
(
0
)