文档介绍：Student:Liufigure,physicsandinformationengineeringcollegesInstructor:XiaoYunhong,JianghanUniversityEveryday,inourworkandinourleisuretime,municationmedia,monbeingthetelephone,radio,television,.municate(nearly)instantaneouslywithpeopleondiffidentcontinents,transactourdailybusiness,,Faraday,Gauss,Maxwell,,,1831,,,’,asensitivedevicethatcoulddevicethatcoulddetectradiosignals,calledthecoherer,municationoveradistanceof150yardsatOxford,,in1897,,1901,MarconireceivedaradiosignalatSignalHillinNewfoundland,whichwastransmittedfromCornwall,England,,(AM)broadcastwasinitiatedin192