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
86
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.
The author of this passage probably intended to explain ,______.
选项
A、exactly how radar works
B、why the British used radio waves in their device
C、how radar(word and device)came to be
D、how radar helped the British win the Battle of Britain
答案
C
解析
该题目是一个主旨题。文章内容是阐述了雷达是一个利用声波原理,使用无线电波制造出来,并在二战中发挥巨大作用的装置。而且,“雷达"是一个制造出来的词,是“无线电探测器"的首字母缩写,所以C项“雷达”如何产生为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/FgLC777K
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
Hethoughtthatthebadworkingconditionswouldresultinthestrikeoftheworkers.
TomandJackhavereturnedbut______studentsofthegrouphaven’tcomebackyet.
You______meyourtelephonenumberincasesomeonewantstocontactyou.
Technicalschoolspreparetheirstudentsfortheapplicationofpracticalskillstheylearninclass______theirwork.
Teachersaresupposedtobepatientandnottolosetheirtempernomatterwhatmistakestheirstudentsmake.
Therearemanyproblemsinourmodernworld.Oneveryseriousproblemisenergy.Wegetagreat【71】ofenergyweneedfromcoal
Therearemanyproblemsinourmodernworld.Oneveryseriousproblemisenergy.Wegetagreat【71】ofenergyweneedfromcoal
Itisafactthatthiscountry’susingupenergyfasterthanweproduceit.
LastnightafterdinnerItoldmyfamilythebadnews.1hadthisclassassignmenttomonitorouruseofenergyathomeforawe
Thebookisa______(humor)accountofayoungman’stravelsinAsia.
随机试题
男性,40岁,3个月前着凉后发热,咯臭黄痰,间断抗感染治疗,胸片示右肺背段有4cm大小的圆形阴影,内可见空洞,诊断男性,25岁,淋雨后高热,胸片示左下肺尖后段斑片影,白细胞增高
男性,50岁。咳嗽。咳痰史10多年,每年持续3月以上,活动后气急2年。病情加重3天。呼吸困难。查体:双肺叩诊过清音。昕诊双肺干湿啰音。该患者主要的治疗是
女,30岁。因出现类似早孕症状两次到某县医院门诊就医,大夫简单检查后均诊断为妇科炎症,但该女士服药多日症状未见缓解。半个月后,因突然阴道大出血和急腹症被送往医院抢救后确诊为异位妊娠。该案例中,初诊医生可能违背的临床诊疗伦理要求是
A.增强CTB.B超C.X线经皮肝穿刺胆道造影(PTC)D.MRIE.经内镜逆行胰胆管造影(ERCP)胆道疾病检查首选()
生产经营单位实行的安全生产奖惩制度,遵循安全生产管理理论中______。
渠道中线圆曲线主点是指()。
关于长期股权投资权益法核算,下列说法中正确的有()。
外部监督的监督主体与监督对象之间不具有直接的行政隶属关系。()
A、 B、 C、 D、 B题干符号的排列规律为:ABCDDCBA。B项符合该规律。
France
最新回复
(
0
)