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
65
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
Thefirstatomicbomb______.TheAmericansdroppedasecondbombinJapan______.
You______meyourtelephonenumberincasesomeonewantstocontactyou.
______isnotknownwhattheydiscussedinthemeeting.
Thedyingmansaid______(vague)tohislawyer,"Iwillleaveallmypropertytotheorphans."
Themountainplaceisbeautiful,but______theworkingconditions,itisterrible.
Althougheachbabyhasanindividualscheduleofdevelopment,generalpatternsofgrowthhavebeenobserved.Threeperiodsofde
AAlikelightBwaves,microwavesCmaybereflectedandDconcentrated.
TheBlacksdemandedthattheirlivingandworkingconditions______.
______canbeproperlycalledaclockalwaysstrikesthehoursandtellsthetime.
随机试题
给定曲线y=x3与直线y=px-q(其中p>0),求p与q为何关系时,直线y=px-q是y=x2的切线。
APTT是反映
患者咳嗽痰白清稀,食少便溏,下肢轻度浮肿,舌淡苔自,脉弱。治疗应选用
不同平面坐标系统间常采用相似变换,其变换一般需要()转换参数,求解转换参数的个数以及至少需要公共点坐标的个数是()。
下列燃烧类型中属于混合燃烧的是()。
为了保护未成年人的身心健康及其合法权益,促进未成年人健康成长,根据《宪法》,我国制定了《中华人民共和国未成年人保护法》。下列描述与《未成年人保护法》不一致的是()。
下列机构属于宪政史上出现的或目前尚存的违宪审查机构的有()。
ReadStephenOverell’sreviewofabookbyFrancesCairncrosscalledTheInsidiousTechRevolution,andthequestionsontheopp
Theabilityoffallingcatstorightthemselvesinmidairandlandontheirfeethasbeenasourceofwonderforages.Biolo
A、Awarenessofthedangersofsmoking.B、Steadyresolvetoquit.C、Groupsupporting.D、Professionalconsultation.C
最新回复
(
0
)