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1、博士研究生入学考试英语全真模拟试题(14)LReadingComprehension(40%)Passage1Microwavesareatypeofelectromagneticradiation;theyareaverymildformofelectricalormagneticwavethatmovesthroughspace・UnlikeX-raysandgammarays,whichareverypowerfulraysofradiation,microwavesareratherweakandaremuchmoreli
2、kethewavesofradiationusedinradiobroadcasting.Inmicrowaveovens,theuseofmicrowaveswithwhichmostpeoplemefamiliar,thewavesareproducedbyanelectronictubecalledamagnetron.Microwavesproduceheatinanyfoodplacedinsidetheovenbycausingthewaterinthefoodtovibraterapidlyandthusheatup
3、.Foodthathavemorewaterinthemtakelesstimetocookandprobablyhavemoreoftheirnutrientsleftintactwhencookedinamicrowaveoven.Microwavesdonotpassthroughmetal,sothemicrowavesareretainedwithintheoven.Microwavespassimmediatelythroughglass,paper,andplasticwithnoeffectonthesemater
4、ialsoronthemicrowaves;nothinginsidethemicrowaveovenisheatedexceptthefooditself,socookingprocessismuchmoreefficientthaninconventionalovens.Sometimesapanorcontainerisheatedbecauseitistouchingthehotfood,though:someusersofmicrowaveovenhavebeenburnedbybutfood,byhotpans,ors
5、teamescapingfromthefood・Nodocumentedcaseofrtidiationburnsbornamicrowaveovenhaseverbeenreported・Actually,weknowverylittleabouthowmicrowaveradiationmightaffecthumanbeings・Obviously,ifmicrowavecancookaroastbyexcitingthewatermoleculesinthemeat,theycoulddothesamethingtohum
6、anflesh.Humanbeingcouldbeburnedbyprolongedexposuretohighlevelsofmicrowaves・Butscientistsaremoreconcernedabouttheeffectsoflowlevelmicrowtiveexposures,suchasmightresultfromaleakingmicrowaveoven.Noresearchhasyetbeenperformedonpeoplewhohavebeenexposedtolowlevelmicrowavera
7、diation.Someexperimentshavebeenperformedonanimals,buttheresultsareverydifficulttointerpret.Astheeyesareparticularlysensitive,rabbitsexposedtolowlevelmicrowaveswerecheckedforthegrowthofcataracts,andnonewerefound.Ontheotherhand,someanimalsseemabletosensemicrowaveradiati
8、onandtrytoescapefromitimmediately.Inothers,microwaveradiationcausesthebodytoreactasifdefendingitselfagainstadecease.Theseres
