双语教案.docx
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双语教案.docx
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双语教案
新课引入:
Review:
(复习)
Well,inourlastlesson,welearnedthelawofuniversalgravitation.Asweknow,everyobjectintheuniverseattractseachotherwithaforce,nowletsreviewtheformulafortheforceofuniversalgravitation.
(上一节课,我们学习了万有引力定律及其应用,首先请同学们回忆一下万有引力定律的表达式。
)
F=G
解释每个量的含义:
Fisthegravitationalforce
m1&m2arethemassesofthetwoobjects
risthedistancebetweentheobjects
Gistheuniversalgravitationalconstant
Becausethegravitationalconstantandmassesofobjectsineverydaylifeareverysmall,
wecan’tfeelthegravitationalforce.Butifthemassesofobjectsareverylarge,theforcewillbefelteasily.Especiallyintheuniverse,gravitationalforceisveryimportant.
(由于引力常量很小,我们日常接触的物体的质量又不是很大,所以我们很难感觉到物体间的引力。
当是如果物体的质量很大,这个引力就非常可观了,特别在天体运动中,万有引力发挥了巨大的作用,有了它天体各个星球间才能有规律的运转。
)
新课教学:
Inthislesson,wewilltalkaboutoursolarsystemandunderstandsomethingsabouttheplanetsinit.Aswealreadyknow,oursolarsystemcontainsnineplanetsandmanycometsandotherobjects.
(本堂课,我们一起来学习一些有关太阳系的知识,了解一下太阳系中各大行星的有关知识。
我们知道太阳系是由9大行星和许许多多的小行星、彗星组成的一个天体系统。
)
Now,Iwanteverygrouptostartadiscussionbasedonthepapersyoujustgotandwhatyoupreparedbeforeclasstogainknowledgeoneveryplanet,especiallytheirdistancesfromthesun,theirsurfacetemperature,diameterandiftheyhavemoons.
(下面请各小组根据课前自己所查资料以及手头的资料展开讨论,了解一下每个行星的有关知识,特别关注一下它们距太阳的距离、表面的温度、直径、是否有卫星等方面的信息。
)
Next,everyonechoosesomeonefromtheirowngrouptocomeupandfillintheblanksfor…
(下面我们请每小组选派一名代表,根据你所掌握的知识来完成下面的表格。
)
下面请同学们来回答下面的问题:
1Ofalltheplanetsinthesolarsystem,whichistheclosesttotheEarthintermsofsizeandmass?
2Whichisthehottestplanetandwhichisthecoldestplanet?
3HowmanyyearsdoesPlutotakeforoneorbitandhowaboutMercury?
4Whichisthesmallestplanet(itissmallerthantheEarth’smoon)?
5Doplanetsgiveofftheirownlight?
Howcanweseethem?
2
3
Mercury、Venus、Earth、andMarsaretheplanetsclosesttothesun.Theyarecalledtheinnerplanets.Theinnerplanetsaremadeupmostlyofrock
(水星、金星、地球、火星、是离太阳最近的四大行星,把他们称为内行星)
Now,someonegiveusasummaryoftheinnerplanets.Everybodyelsewatchthescreenwhilelisteningtothesummary
下面请一位同学对内行星来做一个小结,请大家边听同学小结边看大屏幕了解一下各行星的外观。
Earthisveryimportanttousbecauseitistheplanetthatweliveon,soletswatchashortvideoaboutit.
由于我们人类生活在地球上,关于地球我们来看一段录像的片段。
Next,letslookatapictureofJupiterandSaturn.
下面让我们简单的看一下木星和土星的外观照片
NeptuneandPlutowerediscoveredbyusingthelawofuniversalgravitationalforce.Intheeighteenthcentury,peoplealreadyknewsevenplanetsinoursolarsystem.YDS,astudentofEngland’sCambridgeUniversityandLWLfromFrancewhowasinterestedinastronomy,usedtheinformationtheygainedfromobservationandthelawofuniversalgravitationalforcetocalculatetheorbitofNeptuneandfinallydiscoveredtheplanetin1846.Thesamemethodwasusedin1930tofindtheninthplanetinoursolarsystem,Pluto.
我们再来看看海王星和冥王星的情况
由于海王星,冥王星的发现是应用万有引力定律取得辉煌成就的例子。
在18世纪,人们已经知道太阳系有7个行星。
英国剑桥大学的学生亚当斯和法国的天文爱好者勒维列根据天王星的观测资料,各自独立地根据万有引力定律计算出这颗新行星的轨道,在1846年终于发现了这颗行星。
用同样的方法,在1930年,人们发现了太阳系的第九个行星-----冥王星
ThediscoveryofNeptuneandPlutoprovedtheimportanceofthelawofuniversalgravitation.
海王星、冥王星的发现,显示了万有引力对研究天体运动的重要意义。
Last,letswatchashortvideotopreviewthethingsforourthislesson.
最后让我们用一段录像的片段来总结一下本堂课所学的知识。
请看屏幕
Plant
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
DistancefromtheSun
Inmillionkm
Timeforoneorbit
(y=year,d=day)
Diameterinkm
Averagesurface
temperature
Numberofmoons
Topic:
RefractionofLight
NanjingNo.5MiddleSchoolChangMeixia(南京五中常美霞)
T:
ClassbeginGoodmorningboysandgirls
TodayourtopicisRefractionoflight.Atfirst,let’sdiscussaquestion:
Whatwillhappenifarayapproachesamirror?
S:
Thelightwillbereflected.
T:
Whichlawdoesthereflectionoflightfollow?
S:
ItfollowsTheLawofReflection.
T:
Yes,whenalightrayisincidentuponareflectingsurface,theangleofreflectionisequaltotheangleofincidence.Bothoftheseanglesaremeasuredfromanormal.Theincidentray,thereflectedray,andthenormalalllieinthesameplane.Wecallit“thelawofreflection”.
Usingcomputershowthediagramandthelawwhileteachersaying.
T:
Ifthelightraydidnotapproachtoamirrorbuttoasurfaceofwater,pleaseguesswhatwillhappen?
S:
Someofthelightrayisreflectedbackintoair,theotheristravelingintowater.
T:
Thelightrayinthewaterwillbenearorawayfromthenormalorthedirectionwillnotchange?
Studentsdiscussforamoment.
T:
Let’swatchanexperimentthenwewillknowthefact.
Experiment:
Abundleoflaserincidentfromairintowater.
T:
Whatdoyousee?
S:
Someofthelightrayisreflectedbackintoair,theotheristravelingintowater.
Itbendstowardthenormal.
Teacherusecomputershowthethreelightraysandsay:
Thepathoflightraybendswhentravelingfromonematerialtoanother,suchasfromairtowater,iftheangleofincidenceisnotzerodegree.WecallthisappearanceRefraction.
UsingcomputershowthedefinitionofRefraction:
Refraction
Thechangeindirectionoflightattheboundarybetweentwomaterialsiscallrefraction.
Usingcomputerintroduce“angleofincidence”and“angleofrefraction”
T:
Theanglebetweenincidentrayandnormaliscalled“angleofincidence”.Theanglebetweenrefractedrayandnormaliscalled“angleofrefraction”.Fromtheexperimentandthemodeloflightwealsocanfindthepositionofincidentrayandrefractionray:
Thepositionofincidentrayandrefractionray
Theincidentray、therefractedrayandthenormalalllieinthesameplane.Thenormalliesbetweentheincidentandrefractedray.
showthedirectionoftherayinchangingbyexperiment:
Iftheangleofincidenceiszero,theangleofrefractioniszerotoo.
Iftheangleofincidenceisincrease,theangleofrefractionisincreasetoo.
Iftheangleofincidenceisdecrease,theangleofrefractionisdecreasetoo.
T:
ButtheangleofrefractionisalwayssmallerthantheangleofincidencewhentheraytravelsfromairintowaterIfwerepeattheexperimentuseglassorothertransparentmaterial,wecanacquirethesameconclusion.
Usingcomputershowthelightmodelwhilesaying:
]
Usingcomputershowtheconclusion:
Conclusion:
Therayinthetransparentmaterialisalwaysnearertothenormalthantherayintheair,iftheincidentangleisnotzerodegree.
T:
araytravelsfromairtowater;wecandrawthemodeloflight.Ifarayoflighttravelfromwatertoairandthesecondincidentrayisagainstthefirstrefractedray,whatisthedirectionoftherefractedrayinair?
S:
Itwillbealongtheincidentrayintheair.
Showthediagramusingcomputer:
Conclusion:
Thereversiblequalityofthelight.
T:
Pleasewatchtwopictures:
T:
Whatdoyoufindfromthepictures?
S:
Theperson’slegslookshorterthannormalone’sandthepencilisbroken.
T:
Why?
S:
Thedirectionofthelightraychangeswhenittravelsfromwatertoair.
T:
canyoudrawamodeloflighttodescribethesecondpicture?
Askstudentsdrawitonthepaperandshowoneofthembycomputerandcommentitwithstudents.
Thenteacherdrawstwopicturesusingcomputerquickly:
Conclusion:
Theobjectislookedshallowerthanitactuallyis,whenitisunderthewater.
T:
Weknowthereflectionoflightfollowsthelawofreflection.Haveyouthoughtwhichlawtherefractedrayfollowswhenitbends?
Physicistsinvestigateditforalongtime,until1621,theDutchphysicistWillebrandSnellfoundtherelationshipoftherefractedrayandincidentray.Hemeasuredtheincitedandrefractedangleswhenlighttraveledfromairtoglass.Let’srepeattheexperiment,andrecordthevalues.Canyoufindtheconclusionfromthevalues?
Dotheexperimentandshowthevaluesonebyonebycomputer:
Incitedangle(1
_Refractedangle(2
_(1/(2sin(1/sin(2
100_6.70_1.50
1.49
200
13.30
1.50
1.49
300
9.60
1.53
1.49
400
25.20
_1.59
_1.51
_
_500
_30.70
_1.63
_1.50
_
_600
_35.10
_1.71
_1.51
_
_700
_38.60
_1.81
_1.50
_
_800
_40.60
_1.97
_1.51
The(1、(2and(1/(2showtogether,sin(1/sin(2showfinally.
T:
Fromthetabletheratioofthesinsofanglesofincidenceandrefractionisconstant.
=constant
Snellrepeatedhisexperimentswithdifferentmaterialsandfoundthattheratiowasstillconstant.SnelldiscoveredtherelationshipsoitiscalledSnell’slaworrefractionlaw.
3.Snell’slaw
Arayoflightbendsinsuchawaythattheratioofthesineoftheangleofincidencetothesineoftheangleofrefractionisaconstant.
Theformulais:
=constant
T:
Snellfoundthatithaddifferentconstantwhentherayoflighttraveledfromairtodifferentmaterials.Forexample,iftheraytraveledfromairtowater,theconstantwas1.33;iftheraytraveledfromairtoglass,theconstantis1.50.Sotheratioofthesinsdependsonthecharacterofthematerial.Iftheratioofonematerialisbiggerthantheother,itsabilityofbendinglightisbiggertoo.Soifalightraypassingfromavacuumintoagivenmaterial,thisconstantiscalledtheindexofrefractionforthatmaterial.
Itcanbewritten:
n=
Inthisequationiistheangleofincidence.ristheangleofrefractionandnistheindexofrefractionofthematerial.
“n”ofthematerialisbiggertheabil
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