电子与通信技术专业英语Unit-I-4课件

UnitⅠBasicKnowledgeofElectronics

Lesson4RadioWaves

UnitⅠBasicKnowledgeNewWords(24)electromagnetic[i,lektrəumæɡ'netik]a.

电磁的wavelength['weivleŋθ]

n.波长fundamental[,fʌndə‘mentl]

a.基础的，基本的medium['midiəm]

n.介质，传导体aerial['ɛəriəl]n.天线curvature['kə:vətʃə]n.弯曲,曲率NewWords(24)ionosphere

[ai'ɔnə,sfiə]

n.电离层molecule['mɔlikjul]n.分子ultraviolet[,ʌltrə'vaiələt]a.&n.紫外(线)

的，紫外线辐射radiation[,reidi‘eiʃən]n.辐射,放射,放射线,放射物refract[ri'frækt]vt.(使)折射,测定.…..的折射度earthwards

['ə:θwədz]a.向地的ionosphere

[ai'ɔnə,sfiə]

n.attenuate[ə'tenjueit]v.削弱reflection[re'flekʃən]n.反射；映象intervention[,intə'venʃən]n.干涉intervene[,intə'vi:n]n.&vi.干涉,干预,

介入;干涉obstacles

['ɔbstəkl]n.障碍corresponding[,kɔ:ri'spɔndiŋ]a. 符合的;

一致的;相同的attenuate[ə'tenjueit]v.astronomical[,æstrə‘nɔmikəl]a.天文的，天文学的resonator['rezəneitə]n. 谐振器broadcasting['brɔ:d,kɑ:stiŋ]n.广播navigation[,nævi'ɡeiʃən]n.航海antenna[æn'tenə]n. 天线resonate['rezəneit]v. 调谐astronomical[,æstrə‘nɔmikəl]PhrasesandExpressionsatthespeedof以……的速度PhrasesandExpressionsNotes1.Theyareenergy-carrierswhichtravelatthespeedoflightv,theirfrequencyfandwavelengthbeingrelated,asforanywavemotion,…

它们携带能量且以光速在空气中传播，它们的频率与波长相关，即任何电磁波传播时，……(1)which引出定语从句，修饰energy-carriers；(2)atthespeedof：“以……的速度”如：Heisdrivingthecaratthespeedof100kmanhour.(3)theirfrequencyfandwavelengthbeingrelated是现在分词的独立结构，充当状语。Notes2.Thesmal1eris,thelargerf.波长

越小，频率f越高。重要句型themore…themore…，表示“越……越……”，如文中另一句thehigherthefrequencythegreatertheabsorption（频率越高，能量被吸收得越多）。2.Thesmal1eris,thelarge3.Radiowavescanbedescribedeitherbytheirfrequencyortheirwavelength.

无线电波既能用频率又能用波长来描述。句型either…or…，或者……或者……,如：Eitherhecanstayhomeorgotothemovies.3.Radiowavescanbedescribe4.Buttheformerismorefundamentalsince,unlike(andv),fdoesnotchangewhenthewavestravelfromonemediumtoanother.

但前者更常用，因为频率不象速度，不会因传播媒介的改变而变化。

(1)theformer指theirfrequency；(2)whenthewavestravelfromonemediumtoanother是时间状语从句。4.Buttheformerismorefund5.Thistravelsalongaground,followingthecurvatureoftheearth'ssurface.

这种波按地球表面的曲度，沿地表面传播。句中followingthecurvatureoftheearth'ssurface是现在分词短语，充当状语。5.Thistravelsalongaground6.Thisconsistsoflayersofairmolecules(theD,EandFlayers),stretchingfrom…to500kms,which…bythesun'sultravioletradiation.

电离层由空气分子层组成（包括D、E、F层），位于地球上方80公里到500公里处，它由于太阳紫外线的辐射而失去电子，因而带正电荷。

(1)This指前句中的ionosphere（电离层）；(2)stretchingfrom…to500kms是现在分词短语，充当定语，修饰layersofairmolecules；(3)which…bythesun'sultravioletradiation是非限制性定语从句，修饰airmolecules。6.Thisconsistsoflayersof7.Onstrikingtheearththeskywavebouncesbacktotheionospherewhereitisagaingraduallyrefractedandreturnedearthwardsasifby'reflection'.

反射回地面的天波又从地面反射回电离层，并再次被反射回地面，如“影像”一样。

(1)where引导定语从句，修饰ionosphere；(2)由asif引出的从句asifby'reflection'用虚拟语气，省略了谓语部分wererefracted。7.OnstrikingtheearththesTranslationofTextsLesson4RadioWavesRadiowavesareamemberoftheelectromagneticfamilyofwaves.Theyareenergy-carrierswhichtravelatthespeedoflight（v）,theirfrequency（f）andwavelength（）beingrelated,asforanywavemotion,bytheequationv=fwherev=c=3.0108m/sinavacuum(orair).If=300m,thenf=v/=3.0l08/(3.0102)=106Hz=lMHz.Thesmal1eris,thelargerf.TranslationofTextsLesson4第4课无线电波无线电波是电磁波大家族中的一员，它们携带能量且以光速在空气中传播，它们的频率与波长相关，即任何电磁波传播时，有

v=f

这里，v=c=3.0108m/s（在空气中），如果=300m，则f=v/=3.0l08/(3.0102)=106Hz=lMHz。波长越小，频率f越高。第4课无线电波Radiowavescanbedescribedeitherbytheirfrequencyortheirwavelength.buttheformerismorefundamentalsince,unlike(andv),fdoesnotchangewhenthewavestravelfromonemediumtoanother.

无线电波既能用频率又能用波长来描述。但前者更常用，因为频率不同于速度，它不会因传播媒介的改变而变化。RadiowavescanbedRadiowavescantravelfromatransmittingaerialinoneormoreofthreedifferentways(asshowninFig.4-1).

从天线辐射出去的无线电波通常以三种形式传播（如图4－1所示）。Radiowavescantrave(a)Surfaceorgroundwave.Thistravelsalongaground,followingthecurvatureoftheearth'ssurface.Itsrangeislimitedmainlybytheextenttowhichenergyisabsorbedfromitbytheground.Poorconductorssuchassandabsorbmorestronglythatwater,andthehigherthefrequencythegreatertheabsorption.Therangemaybeabout1,500kmatlowfrequencies(longwave，butmuchlessforv.h.f).(a)Surfaceorgrou

（a）地表波或地波这种波按地球表面的曲度，沿地表面传播。它的传播范围有限，其能量被地表面吸收，恶劣的地形条件如沙漠比水面更易吸收能量，频率越高，能量被吸收得越多。低频波（长波）的传播范围约为1500公里。高频波的传播范围要小得多。（a）地表波或地波这种波按地球表面的曲(b)Skywave.Thistravelsskywardsand,ifitisbelowacertaincriticalfrequency(typically30MHz),isreturnedtoearthbytheionosphere.Thisconsistsoflayersofairmolecules(theD,EandFlayers),stretchingfromabout80kmabovetheearthto500km,whichhavebecomepositivelychargedthroughtheremovalofelectronsbythesun'sultravioletradiation.Onstrikingtheearththeskywavebouncesbacktotheionospherewhereitisagaingraduallyrefractedandreturnedearthwardsasifby'reflection'.Thiscontinuesuntilitiscompletelyattenuated.(b)Skywave.This

（b）天波沿天空传播，若低于某个关键频率（如30MHz），会被电离层反射回地面。电离层由空气分子层组成（包括D、E、F层），位于地球上方80公里到500公里处，它由于太阳紫外线的辐射而失去电子，因而带正电荷。反射回地面的天波又从地面反射回电离层，并再次被反射回地面，如此反复多次直到能量完全衰减。（b）天波沿天空传播，若低于某个关键频(c)Spacewave.Forv.h.f.,u.h.f.andmicrowavesignals,onlythespacewave,givingline-of-sighttransmission,iseffective.Arangeofupto150kmispossibleonearthifthetransmittingaerialisonhighgroundandtherearenointerveningobstaclessuchashills,buildingsortrees.(c)Spacewave.Forv

（c）空间波甚高频、超高频和微波只能以空间波的形式才能有效传播，空间波也称视距传播。如果天线架设很高且没有障碍阻隔，如高山、建筑物、大树等，空间波的传播距离可达150公里。（c）空间波甚高频、超高频和微波只能以Radiowaveshavefrequenciesfrom300GHztoaslowas3Hz,andcorrespondingwavelengthsfrom1millimeterto100kilometers.Likeallotherelectromagneticwaves,theytravelatthespeedoflight.Naturallyoccurringradiowavesaremadebylightning,orbyastronomicalobjects.Artificiallygeneratedradiowavesareusedforfixedandmobileradiocommunication,broadcasting,radarandothernavigationsystems,satellitecommunication,computernetworksandinnumerableotherapplications(asshowninFig.4-2).Radiowaveshavefreq

无线电波频率从300兆赫到3赫兹，相应的波长从1毫米到100公里。像其他所有的电磁波一样，它们以光速传播。自然产生的无线电波是由闪电或天体形成。人工产生的无线电波用于固定和移动无线电通讯，广播，雷达和其他导航系统以及卫星通信，计算机网络及无数其他应用（如图4－2所示）。无线电波频率从300兆赫到3赫兹，相应Inordertoreceiveradiosignals,forinstancefromAM/FMradiostations,aradioantennamustbeused.However,sincetheantennawillpickupthousandsofradiosignalsatatime,aradiotunerisnecessarytotuneintoaparticularfrequency(orfrequencyrange).Thisistypicallydoneviaaresonator(initssimplestform,acircuitwithacapacitorandaninductor).Theresonatorisconfiguredtoresonateataparticularfrequency(orfrequencyband),thusamplifyingsinewavesatthatradiofrequency,whileignoringothersinewaves.Usually,eithertheinductororthecapacitoroftheresonatorisadjustable,allowingtheusertochangethefrequencyatwhichitresonates.Inordertoreceiv

为接收无线电信号，例如从调幅/调频广播电台接收信号，必须使用无线天线。然而，由于天线可以同时接收数以千计的广播信号，必须有一个无线电调谐器调整到一个特定的频率（或频率范围）。这通常是通过谐振器实现的（其最简单的形式是一个由电容和电感组成的电路）。谐振器被设置在某个特殊频率（或频段），从而放大那个具有特殊频率的正弦波，而忽略其他无线电波。通常，谐振器的电感或电容都是可调的，允许用户对谐振器改变频率进行调谐。为接收无线电信号，例如从调幅/调频广播电Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.Exercisesa.Radiowavesareenergy-carrierswhichtravelatthespeedoflight(v),theirfrequency(f)andwavelength().b.Radiowavescanbedescribedbytheirfrequencyratherthanwavelength.a.Radiowavesareenergy-carrc.Thefrequencyoftheradiowavesismorefundamentalthanwavelengthsince,unlike(andv),fdoesnotchangewhenthewavestravelfromonemediumtoanother.d.Radiowavescantravelfromatransmittingaerialinoneormoreofthreedifferentways.c.Thefrequencyoftheradioe.Itsrangeisnolimitedbytheextenttowhichthegroundabsorbsenergyfromit.f.Poorconductorssuchassandabsorbmorestronglythanwater,andthehigherthefrequencythegreatertheabsorption.e.Itsrangeisnolimitedby2.Matchthefollowingtermstoappropriatedefinitionorexpression.2.Matchthefollowingtermstoa.Radiowaves1.sandb.Surfaceorgroundwave2.thewavetravelsalongaground,followingthecurvatureoftheearth'ssurfacec.Skywave3.thewavegivingline-of-sighttransmissiond.Spacewave4.thewavetravelsskywards,ifbelowacertaincriticalfrequencyisreturnedtoearthe.Poorconductors5.amemberoftheelectromagneticfamilyofwavesa.Radiowaves3.Fillinthemissingwordsaccordingtothetext.3.Fillinthemissingwordsaca.Inavacuum(orair)，if=300m,thenf=v/=_______________=106Hz=lMHz.Thesmalleris,thelargerf.

a.Inavacuum(orair)，if=b.Therangemaybeabout________kmatlowfrequencies(longwave;butmuchlessforv.h.f).b.Therangemaybeabout____c.Thisconsistsoflayersofairmolecules(theD,EandFlayers),stretchingfromabout_____kmabovetheearthto_______km,whichhavebecomepositivelychargedthroughtheremovalofelectronsbythesun'sultravioletradiation.c.Thisconsistsoflayersofd.Arangeofupto150kmsispossibleonearthifthe_________________isonhighgroundandtherearenointerveningobstaclessuchashills,buildingsortrees.d.Arangeofupto150kmsis4.TranslatethefollowingparagraphsintoChinese.

4.Translatethefollowingpar(a)Surfaceorgroundwave.Thistravelsalongaground,followingthecurvatureoftheearth'ssurface.Itsrangeislimitedmainlybytheextenttowhichthegroundabsorbsenergyfromit.Poorconductorssuchassandabsorbmorestronglythanwater,andthehigherthefrequencythegreatertheabsorption.Therangemaybeabout1,500kmatlowfrequencies(longwave;butmuchlessforv.h.f).(a)Surfaceorground(b)Skywave.Thistravelsskywardsand,ifitisbelowacertaincriticalfrequency(typically30MHz),isreturnedtoearthbytheionosphere.Thisconsistsoflayersofairmolecules(theD,EandFlayers),stretchingfromabout80kmabovetheearthto500km,whichhavebecomepositivelychargedthroughtheremovalofelectronsbythesun'sultravioletradiation.Onstrikingtheearththeskywavebouncesbacktotheionospherewhereitisagaingraduallyrefractedandreturnedearthwardsasifby'reflection'.Thiscontinuesuntilitiscompletelyattenuated.(b)Skywave.Thist(c)Spacewave.Forv.h.f.,u.h.f.andmicrowavesignals,onlythespacewave,givingline-of-sighttransmission,iseffective.Arangeofupto150kmsispossibleonearthifthetransmittingaerialisonhighgroundandtherearenointerveningobstaclessuchashills,buildingsortrees.(c)Spacewave.ForEndEndUnitⅠBasicKnowledgeofElectronics

Lesson4RadioWaves

UnitⅠBasicKnowledgeNewWords(24)electromagnetic[i,lektrəumæɡ'netik]a.

电磁的wavelength['weivleŋθ]

n.波长fundamental[,fʌndə‘mentl]

a.基础的，基本的medium['midiəm]

n.介质，传导体aerial['ɛəriəl]n.天线curvature['kə:vətʃə]n.弯曲,曲率NewWords(24)ionosphere

[ai'ɔnə,sfiə]

n.电离层molecule['mɔlikjul]n.分子ultraviolet[,ʌltrə'vaiələt]a.&n.紫外(线)

的，紫外线辐射radiation[,reidi‘eiʃən]n.辐射,放射,放射线,放射物refract[ri'frækt]vt.(使)折射,测定.…..的折射度earthwards

['ə:θwədz]a.向地的ionosphere

[ai'ɔnə,sfiə]

n.attenuate[ə'tenjueit]v.削弱reflection[re'flekʃən]n.反射；映象intervention[,intə'venʃən]n.干涉intervene[,intə'vi:n]n.&vi.干涉,干预,

介入;干涉obstacles

['ɔbstəkl]n.障碍corresponding[,kɔ:ri'spɔndiŋ]a. 符合的;

一致的;相同的attenuate[ə'tenjueit]v.astronomical[,æstrə‘nɔmikəl]a.天文的，天文学的resonator['rezəneitə]n. 谐振器broadcasting['brɔ:d,kɑ:stiŋ]n.广播navigation[,nævi'ɡeiʃən]n.航海antenna[æn'tenə]n. 天线resonate['rezəneit]v. 调谐astronomical[,æstrə‘nɔmikəl]PhrasesandExpressionsatthespeedof以……的速度PhrasesandExpressionsNotes1.Theyareenergy-carrierswhichtravelatthespeedoflightv,theirfrequencyfandwavelengthbeingrelated,asforanywavemotion,…

它们携带能量且以光速在空气中传播，它们的频率与波长相关，即任何电磁波传播时，……(1)which引出定语从句，修饰energy-carriers；(2)atthespeedof：“以……的速度”如：Heisdrivingthecaratthespeedof100kmanhour.(3)theirfrequencyfandwavelengthbeingrelated是现在分词的独立结构，充当状语。Notes2.Thesmal1eris,thelargerf.波长

越小，频率f越高。重要句型themore…themore…，表示“越……越……”，如文中另一句thehigherthefrequencythegreatertheabsorption（频率越高，能量被吸收得越多）。2.Thesmal1eris,thelarge3.Radiowavescanbedescribedeitherbytheirfrequencyortheirwavelength.

无线电波既能用频率又能用波长来描述。句型either…or…，或者……或者……,如：Eitherhecanstayhomeorgotothemovies.3.Radiowavescanbedescribe4.Buttheformerismorefundamentalsince,unlike(andv),fdoesnotchangewhenthewavestravelfromonemediumtoanother.

但前者更常用，因为频率不象速度，不会因传播媒介的改变而变化。

(1)theformer指theirfrequency；(2)whenthewavestravelfromonemediumtoanother是时间状语从句。4.Buttheformerismorefund5.Thistravelsalongaground,followingthecurvatureoftheearth'ssurface.

这种波按地球表面的曲度，沿地表面传播。句中followingthecurvatureoftheearth'ssurface是现在分词短语，充当状语。5.Thistravelsalongaground6.Thisconsistsoflayersofairmolecules(theD,EandFlayers),stretchingfrom…to500kms,which…bythesun'sultravioletradiation.

电离层由空气分子层组成（包括D、E、F层），位于地球上方80公里到500公里处，它由于太阳紫外线的辐射而失去电子，因而带正电荷。

(1)This指前句中的ionosphere（电离层）；(2)stretchingfrom…to500kms是现在分词短语，充当定语，修饰layersofairmolecules；(3)which…bythesun'sultravioletradiation是非限制性定语从句，修饰airmolecules。6.Thisconsistsoflayersof7.Onstrikingtheearththeskywavebouncesbacktotheionospherewhereitisagaingraduallyrefractedandreturnedearthwardsasifby'reflection'.

反射回地面的天波又从地面反射回电离层，并再次被反射回地面，如“影像”一样。

(1)where引导定语从句，修饰ionosphere；(2)由asif引出的从句asifby'reflection'用虚拟语气，省略了谓语部分wererefracted。7.OnstrikingtheearththesTranslationofTextsLesson4RadioWavesRadiowavesareamemberoftheelectromagneticfamilyofwaves.Theyareenergy-carrierswhichtravelatthespeedoflight（v）,theirfrequency（f）andwavelength（）beingrelated,asforanywavemotion,bytheequationv=fwherev=c=3.0108m/sinavacuum(orair).If=300m,thenf=v/=3.0l08/(3.0102)=106Hz=lMHz.Thesmal1eris,thelargerf.TranslationofTextsLesson4第4课无线电波无线电波是电磁波大家族中的一员，它们携带能量且以光速在空气中传播，它们的频率与波长相关，即任何电磁波传播时，有

v=f

这里，v=c=3.0108m/s（在空气中），如果=300m，则f=v/=3.0l08/(3.0102)=106Hz=lMHz。波长越小，频率f越高。第4课无线电波Radiowavescanbedescribedeitherbytheirfrequencyortheirwavelength.buttheformerismorefundamentalsince,unlike(andv),fdoesnotchangewhenthewavestravelfromonemediumtoanother.

无线电波既能用频率又能用波长来描述。但前者更常用，因为频率不同于速度，它不会因传播媒介的改变而变化。RadiowavescanbedRadiowavescantravelfromatransmittingaerialinoneormoreofthreedifferentways(asshowninFig.4-1).

从天线辐射出去的无线电波通常以三种形式传播（如图4－1所示）。Radiowavescantrave(a)Surfaceorgroundwave.Thistravelsalongaground,followingthecurvatureoftheearth'ssurface.Itsrangeislimitedmainlybytheextenttowhichenergyisabsorbedfromitbytheground.Poorconductorssuchassandabsorbmorestronglythatwater,andthehigherthefrequencythegreatertheabsorption.Therangemaybeabout1,500kmatlowfrequencies(longwave，butmuchlessforv.h.f).(a)Surfaceorgrou

（a）地表波或地波这种波按地球表面的曲度，沿地表面传播。它的传播范围有限，其能量被地表面吸收，恶劣的地形条件如沙漠比水面更易吸收能量，频率越高，能量被吸收得越多。低频波（长波）的传播范围约为1500公里。高频波的传播范围要小得多。（a）地表波或地波这种波按地球表面的曲(b)Skywave.Thistravelsskywardsand,ifitisbelowacertaincriticalfrequency(typically30MHz),isreturnedtoearthbytheionosphere.Thisconsistsoflayersofairmolecules(theD,EandFlayers),stretchingfromabout80kmabovetheearthto500km,whichhavebecomepositivelychargedthroughtheremovalofelectronsbythesun'sultravioletradiation.Onstrikingtheearththeskywavebouncesbacktotheionospherewhereitisagaingraduallyrefractedandreturnedearthwardsasifby'reflection'.Thiscontinuesuntilitiscompletelyattenuated.(b)Skywave.This

（b）天波沿天空传播，若低于某个关键频率（如30MHz），会被电离层反射回地面。电离层由空气分子层组成（包括D、E、F层），位于地球上方80公里到500公里处，它由于太阳紫外线的辐射而失去电子，因而带正电荷。反射回地面的天波又从地面反射回电离层，并再次被反射回地面，如此反复多次直到能量完全衰减。（b）天波沿天空传播，若低于某个关键频(c)Spacewave.Forv.h.f.,u.h.f.andmicrowavesignals,onlythespacewave,givingline-of-sighttransmission,iseffective.Arangeofupto150kmispossibleonearthifthetransmittingaerialisonhighgroundandtherearenointerveningobstaclessuchashills,buildingsortrees.(c)Spacewave.Forv

（c）空间波甚高频、超高频和微波只能以空间波的形式才能有效传播，空间波也称视距传播。如果天线架设很高且没有障碍阻隔，如高山、建筑物、大树等，空间波的传播距离可达150公里。（c）空间波甚高频、超高频和微波只能以Radiowaveshavefrequenciesfrom300GHztoaslowas3Hz,andcorrespondingwavelengthsfrom1millimeterto100kilometers.Likeallotherelectromagneticwaves,theytravelatthespeedoflight.Naturallyoccurringradiowavesaremadebylightning,orbyastronomicalobjects.Artificiallygeneratedradiowavesareusedforfixedandmobileradiocommunication,broadcasting,radarandothernavigationsystems,satellitecommunication,computernetworksandinnumerableotherapplications(asshowninFig.4-2).Radiowaveshavefreq

无线电波频率从300兆赫到3赫兹，相应的波长从1毫米到100公里。像其他所有的电磁波一样，它们以光速传播。自然产生的无线电波是由闪电或天体形成。人工产生的无线电波用于固定和移动无线电通讯，广播，雷达和其他导航系统以及卫星通信，计算机网络及无数其他应用（如图4－2所示）。无线电波频率从300兆赫到3赫兹，相应Inordertoreceiveradiosignals,forinstancefromAM/FMradiostations,aradioantennamustbeused.However,sincetheantennawillpickupthousandsofradiosignalsatatime,aradiotunerisnecessarytotuneintoaparticularfrequency(orfrequencyrange).Thisistypicallydoneviaaresonator(initssimplestform,acircuitwithacapacitorandaninductor).Theresonatorisconfiguredtoresonateataparticularfrequency(orfrequencyband),thusamplifyingsinewavesatthatradiofrequency,whileignoringothersinewaves.Usually,eithertheinductororthecapacitoroftheresonatorisadjustable,allowingtheusertochangethefrequencyatwhichitresonates.Inordertoreceiv

为接收无线电信号，例如从调幅/调频广播电台接收信号，必须使用无线天线。然而，由于天线可以同时接收数以千计的广播信号，必须有一个无线电调谐器调整到一个特定的频率（或频率范围）。这通常是通过谐振器实现的（其最简单的形式是一个由电容和电感组成的电路）。谐振器被设置在某个特殊频率（或频段），从而放大那个具有特殊频率的正弦波，而忽略其他无线电波。通常，谐振器的电感或电容都是可调的，允许用户对谐振器改变频率进行调谐。为接收无线电信号，例如从调幅/调频广播电Exercises1.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.Exercisesa.Radiowavesareenergy-carrierswhichtravelatthespeedoflight(v),theirfrequency(f)andwavelength().b.Radiowavescanbedescribedbytheirfrequencyratherthanwavelength.a.Radiowavesareenergy-carrc.Thefrequencyoftheradiowavesismorefundamentalthanwavelengthsince,unlike(andv),fdoesnotchangewhenthewavestravelfromonemediumtoanother.d.Radiowavescantravelfromatransmittingaerialinoneormoreofthreedifferentways.c.Thefrequencyoftheradioe.Itsrangeisnolimitedbytheextenttowhichthegroundabsorbsenergyfromit.f.Poorconductorssuchassandabsorbmorestronglythanwater,andthehigherthefrequencythegreatertheabsorption.e.Itsrangeisnolimitedby2.Matchthefollowingtermstoappropriatedefinitionorexpression.2.Matchthefollowingtermstoa.Radiowaves1.sandb.Surfaceorgroundwave2.thewavetravelsalongaground,followingthecurvatureoftheearth'ssurfacec.Skywave3.thewavegivingline-of-sighttransmissiond.Spacewave4.thewavetravelsskywards,ifbelowacertaincr