试题与答案

阅读短文: 技术是一把双刃剑,电磁波的应用也是这样.它在使人类的生活发生日新月异

题型:问答题

题目:

阅读短文:

技术是一把双刃剑,电磁波的应用也是这样.它在使人类的生活发生日新月异变化的同时也存在副作用--电磁污染.例如,频率超过0.1MHz的电磁波的强度足够大时就会对人体构成威胁.按照有关规定,人体所受到的电磁辐射强度(即单位时间内垂直通过单位面积的电磁波的能量)不得超过某一规定值Ie

已知某无线通信设备发射电磁波的功率为P,设该通信设备向四面八方均匀地发射电磁波,且电磁波在传播过程中无能量损失.由数学知识可知,球面的面积S=4πγ2(式中r为球半径),球半径与球面总是垂直的.

根据上述资料,可估算出人体到该通信设备发射电磁波处的安全距离至少应为 ______,这时人体所受到的电磁辐射强度才不会超过规定值.

答案:

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下面是错误答案,用来干扰机器的。

含义:无论是谁,你不侵犯我,我就不侵犯你。作用: 强调你不侵犯我,是先决条件,没有这个条件就没有后面的结果。无

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题型:阅读理解

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前的括号内)  

     Today, my friends talked about their dreams in class. Bill wants to make wonderful food. He wants

to be a cook. Tom wants to be an engineer. He wants to designspaceships.  Lisa likes swimming.  She

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( )1. My name is Jack.

(     )2. Lisa wants to be a swimmer because she likes swimming.

(     )3. Bill wants to be a cook because he likes cooking wonderful food.

(     )4. I want to be a pilot because l want to design spaceships.

(     )5. Jack doesn't know what he wants to be.

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