《信息的傳遞》單元測試題二（參考答案）

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8、TTOM: 0cm一、選擇題1-14：D D C A C C A C D A A D D D二、填空題15電磁16增大 等于 3×1085.71“5.7亦可 17機(jī)械能 電磁波18紫外線 紅外線 X射線 無線電波19增強(qiáng) 減弱20電磁波 激21 三、簡答與實(shí)驗(yàn)題22(1)收音時(shí)機(jī)發(fā)出咔咔嚓嚓的聲音。這是因?yàn)閷?dǎo)線頭在銼面上滑動時(shí) ,產(chǎn)生了變化的電流 ,向空中激起了電磁波。2開啟冰箱門時(shí)會聽到收音機(jī)也發(fā)出“咔咔嚓嚓的聲音23接收衛(wèi)星傳來的信號。光纜通信的主要優(yōu)點(diǎn)：容量大 ,不怕雷擊 ,不受電磁干擾 ,通信質(zhì)量高 ,保密性好。(2)開、關(guān)日光燈時(shí) ,產(chǎn)生了變化的電流 ,周圍空間就存在電磁波 ,電視機(jī)接收以后 ,會在電視機(jī)畫面上出現(xiàn)雪花點(diǎn)。四、閱讀與計(jì)算題24C 3×108具有 三 微波爐的外殼用不銹鋼等金屬材料制成 ,可以阻