Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
�1
Name:________________________________________________Period:___________
CanIBelieveMyEyes?
PhysicalScience1
Lightwaves,theirroleinsightandinteracAonswithmaBer
�2
Name:_____________________________________________________________Period:___________
Lesson Page Score Notes
Lesson1.1 6 01234
Lesson1.2 10 01234
Lesson2.1 14 01234
Read2.2 16 01234
Lesson3.1 18 01234
Lesson3.2 20 01234
Read3.3 22 01234
Lesson4.1 26 01234
Read4.2 28 01234
Lesson4.3 30 01234
Read4.4 32 01234
Lesson5.1 34 01234
Lesson5.2 38 01234
Read5.3 40 01234
Lesson6.1 44 01234
Read6.2 46 01234
Lesson6.3 48 01234
Read6.4 49 01234
Read6.5 55 01234
Lesson7.1 58 01234
Lesson7.2 62 01234
Lesson7.3 64 01234
Lesson7.4 66 01234
Lesson7.5 68 01234
Read7.6 70 01234
Read7.7 73 01234
Lesson8.1 78 01234
Lesson8.2 82 01234
Lesson8.3 84 01234
Lesson8.4 86 01234
Lesson8.5 88 01234
Read8.6 90 01234
�1
Lesson Page Score Notes
Lesson9.1 94 01234
Lesson9.2 96 01234
Read9.3 98 01234
Lesson9.4 100 01234
Lesson9.5 102 01234
Lesson9.6 104 01234
Read9.7 106 01234
Lesson10.1 108 01234
Lesson10.2 110 01234
Lesson10.3 112 01234
Read10.4 114 01234
Lesson11.1 117 01234
Read11.2 119 01234
Read11.3 121 01234
Read11.4 126 01234
Read11.5 128 01234
Lesson12.1 130 01234
Read12.2 132 01234
Lesson12.3 136 01234
Lesson13.1 138 01234
Read13.2 140 01234
Lesson13.3 144 01234
PointsDescripAon
1-Mostoftheworkisincomplete.Manyresponsesareunclear,imprecise,andlackimportantdetails.2-Approximatelyhalfoftheworkiscomplete.Mostresponsesarecompleteandclear3-Mostworkiscomplete.Mostresponsesarecompleteandclear.4-Allworkiscomplete.Mostresponsesarecompleteandclear.
Comments
CS-NeedscompletesentenceswithquesConstemsI-IncompleteE-NeedtoprovideevidenceforexplanaCons.T-Verythoroughandwellthoughtout.
�2
Lesson QuesAon Whatdidwedo?
�3
EvidenceGained Whatdidwelearn?
�4
Vocabulary DefiniAons/Images
�5
ScienAficPrinciples
�6
Lesson1–HowdoesaSolarOvenwork?Lesson1.1–Howdoesasolarovenwork?
Whatwillwedo?WewillobserveasolarovenandpredicthowitgetssomuchhoLerthenthesurroundingair.
PredicAon:
Whatpartsofasolarovenallowittoheatupsomuch?
Procedure-Part1Observeimagesofsolarovens.Listthepartsoftheovenandwhyyouthinktheyareimportant.
Procedure-Part2Inpart2youarenowgoingtobuildyourownpizzaboxoven!
Drawaoneinchborderonallfoursidesofthetopofthepizzabox.Cutalongthreesidesleavingthelinealongthebackoftheboxuncut.
Conclusion
1. Whydoyouthinkweusedblackpaperinsidethebox?
Solar Oven Part Why is it important?
Diagram#1
�7
DiscusswithyourgroupthedesignandmaterialsneededforyoursolarovenDrawadraTofyourproposedsolarovenandlabeleachpartanditsfuncCon(whatdoesitdo?)
Discussyourdesignwithyourteacherandgetastampfromyourteacher
Wheneachgroupmemberhasastamp,gatheryourmaterialsandbeginbuilding
�8
�9
�10
Lesson1.2–TesAngyouroven
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewilltakeourovenoutsideandseehowfastitheatsup.
PredicAon:
Howhotdoyouthinkyourovenwillbe?
Safety
• Neverlookdirectlyatthesun!BecarefulaboutthesunreflecCngoffthealuminumfoilaswell!Bothofthesecandamageyoureyes.
ProcedureGetathermometerandinsertthemetalporConthroughthecardboardonthehingesideoftheovensothatthemetalprobeisinsidetheoven.RecordyouriniCaltemperature(Cme0)beforeyouplaceyouroveninthesun.Takeyourovenoutsideandplaceitonthegroundfacingthesun.Tiltyourlidsothesunlightfromthealuminumfoilgoesintoyouroven.StartyourCmerandrecordthetemperatureeveryminutefor10minutes..
Data
Time in Minutes
Temperature in ºC
0
1
2
3
4
5
6
7
8
9
10
�11
Conclusion
1. Howmuchdidyoursolarovenheatup?(TakethefinaltemperatureandsubtracttheiniCaltemperature).
2. Howdoesyourovencomparetootherovensinyourclass?ExplainwhyyourovenisbeLerorworsecomparedtoothers.
3. Comeupwiththreechangesyoucouldmaketoimproveyouroven.Foreach,explainwhyyouthinkitwouldimproveyourresults.
�12
�13
�14
Lesson2–WhatcanopAcalillusionsteachus?Lesson2.1–Whatisgoingonwiththesepictures?
Whatwasthepointofthelastunit?
Whatwillwedo?Wewillobservetwostrangeimages.Bytheendoftheunit,wewillbeabletoexplainhowtheseimageswork.
ProcedureLookatthefirstimageyourteacherprojects.Whatdoyousee?RecordyourobservaConsinthedatatable.Yourteacherwillprojectasecondimage.Whichsquareappearsdarkertoyou,squareAorsquareB?Recordwhatyouseeinthedatatable.Yourteacherwillmakesomechangestothesecondimage.Whichsquareappearsdarkernow,squareAorsquareB?RecordyourobservaCons.
Data
Conclusion
1. WhatdidyounoCceaboutthecirclesinthefirstimage?
2. Doyouthinkwhathappenedwasreal?Howdoyouknow?
Image Observations
First Image
Second Image
Second Image after masks
�15
3.WhydoyouthinkthatsquareAandsquareBlookeddifferentthefirstCmeyoulookedatthemthantheydidthesecondCmeyoulookedatthem?
4.AskingandexploringtheanswerstoquesConsisimportanttoscience.DoesthisacCvitymakeyouthinkofanyquesConsaboutlightoraboutthingsyousee?ListyourquesConsinthefollowingspace.
�16
Reading2.2–LookatThis
Ge`ngReadyThepictureshowstwobentrectangles.Whichbentrectangleislonger?Nowusearulertomeasurethesizeofthetwobentrectangles.Wereyoucorrect?Tomostpeople,BlookslongerthanA.Whenyoumeasured,youmighthavelearnedthatyourguesswaswrong.Inthisreading,youwilllearnhowyourbraincangetconfusedbywhatyoureyessee.Youwillbeabletocomparethefiguresinthisreadingtowhatyousawinclass.Tocomparemeanstothinkaboutwhatisalikeandwhatisdifferent.Asyouread,thinkaboutwhatissimilaranddifferentaboutthelightboxandthepicturesinthisreading.WhatAreOpAcalIllusions?Lookatthesepictures.Stareatthesmalldotinthecenterofthecircles.Nowmovethepictureclosertoyouwhileyoukeeplookingatthedot.Whathappens?TrickslikethesearecalledopCcalillusions.OpCcalisawordrelatedtoyoursenseofsight.Manyotherwordsstartwiththeprefixopt-.Anoptometristisaneyedoctor.Ifyouneedglasses,anopCcianmayhavehelpedyouchooseyourglasses.Youmayhaveseenmagicianswhoperformillusions.Magiciansdonotreallymakethingsdisappear.Buttheydoknowhowtofoolyourbrainsoyouthinkthingsdisappear.OpCcalillusionscanbefunbecausetheyfoolyou.OpCcalillusionsareakindoftrick.Youreyesplayanimportantroleinseeing.Butyoureyesandyourbrainworktogether.Yourbrainistheorganthatmakessenseofwhatyousee.InthepictureintheGecngReadingsecCon,youreyesseetwoidenCcalbentrectangles.Youreyesseetherightthing,butyourbraininterpretsitwrong.Whenyourbraingetsitwrong,thisiscalledanillusion.OpCcalillusionsandmagician’stricksarenotreal.Yourbrainisjustfooled.AnotherOpAcalIllusionLookatthesesmalldarksquares.Ifyoulookcloselyforafewseconds,youwillseelightgraycirclesinbetweenthesquares.Arethegraycirclesreallythere,ordotheyjustseemtobethere?Thisisanotherexampleofanillusion.Yourbrainisbeingfooledagain.CanYouFigureThisOut?HereisonemoreinteresCngimage.LookatthelinesseparaCngtherowsofblackandwhitesquares.Doyouthinkwhatyouareseeingisanillusion?Arethelines
�17
actuallyparallelandyourbrainisbeingfooled,orarethelinesreallyatangles?WeretheImagesinClassOpAcalIllusions?Inclass,yousawstrangeimages.Thefirstlookedlikeabunchofspinningcircles.ThesecondimagelookedlikeacheckerboardwithasquaremarkedAbeingclearlydarkerthananothersquaremarkedB.Finally,yourteacheraddedblackrectanglestothesecondimageanditbecameapparentthatsquaresAandBhadactuallyidenCcaldarkness.Theseimagessucceededinfoolingyourbrain.Theywereillusions.Youobservedarealphenomenon.Whatyousawdependedonchangesinthelight.Aphenomenonisaneventthathappensintherealworldandthatoccursoverandoveragain.SomeCmesyoucanobservethingsthatappearverystrangebutareactuallyreal.Forexample,haveyoueverseenthemoondisappearinthemiddleofthenighteventhoughitisabovethehorizonandtherearenocloudsinthesky?HoldtheCpsofyourthumbandindexfingernexttoeachothersothattheyarejustabouttouching.Holdthemupsothattheyarenexttoyoureyeandlookbetweenthematabrightwhitebackground.Youshouldjustbarelyfeelyourthumbtouchingyourfinger.Youshouldseeoneormoresmallblacklinesbetweenyourfingers.Fromwheredidtheselinescome?Thisisarealthingyouareseeing,notanillusion.Yourbrainisnotgecnganythingwrong.Thisgoalinthisunitistofigureoutwhathappenstomakepeopleseethings,whethertheyarerealorillusions.InvesCgaCngphenomenawillhelpyoulearnhowlightaffectswhatyousee.Inscienceclass,youwillobservedifferentphenomenaalmosteveryday.Bytheendoftheunit,youmaybeabletoexplainhowyoucouldseethetwoimagesfromclass.ObservingtheTwoIllusionsinClassAnimportantpartofscienceismakingobservaCons.AnobservaConistheactofpayingcarefulaLenContoeventsthathappenintheworld.Thisiswhatyoudidinclass.YoupaidcloseaLenContowhatyoucouldseewhenyoulookedatthetwoimages.MakinggoodobservaCons,pluslearningthesciencethatgoeswiththem,willhelpyoutoexplainthingsthathappenaroundyou.WhatQuesAonsDoYouHave?ListquesConsyouhaveaboutlight,seeing,oraboutthetwoimagesfromclassnowthatyouhavefinishedreading.
WhyIsLightImportant?Youalreadyknowthatlighthelpsyousee.Butdidyouknowthatifyouunderstandthebehavioroflight,youcanalsounderstandhowcellphonesandmicrowaveovenswork?ThescienCficideasthatexplainthebehavioroflightalsoexplainhowcomputers,televisions,satellites,GPS,andmanyothersystemswork.Infact,manyscienCficdiscoveriesfromthelast100yearsarebasedonthesameprinciplesthatexplainthebehavioroflight.Youwillnotstudyalloftheseinclass,butyouwilllearnaboutmanyofthem.YoumightalsodecidetoinvesCgateotherusesoflightonyourown.Youmaybesurprisedtolearnthatlightplaysanimportantroleinjustabouteverythingaroundyou.
�18
Lesson3–WhatDoWeNeedtoSeeanObject?Lesson3.1–Probingideas:Seeingobjectsaroundtheroom.
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillexploresomeofthethingshumansneedinordertosee.Wewilltrytoex-plainwhywecanseesomeobjectsbutnotothers.
ProcedureLookattheimageyourteacherprojects.Whycanthegirlseethetree?
Lookattheimageyourteacherprojects.Whydoesn’tthegirlseethecar?
Asyourteachernamesobjectsintheroom,recordtheminthedatatable.Thenputacheckmark(✓)intheappropriatecolumn.Youwillnotbeabletoseeeverythingyourteachernames.ItisimportantthatyoukeepyourbodyandyoureyesinthesameposiConasyoucollectdata.
Objects around the Classroom I Can See I Cannot See
�19
Conclusion
1. Whatfactorsaffectwhetheryoucanseeanobjectornot?
�20
Lesson3.2–DeterminingthecondiAonsforsight-thelightbox.
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillgatherevidenceaboutwhatneedstohappeninorderforpeopletoseeanobject.
ProcedureFollowyourteacher’sdirecCons.RecordyourobservaConsfromeachstepbeforeyoumoveontothenextstep.
Lookintothelightbox.Besurethelidandtheflapremainclosed.Inthedatatable,drawwhatyousee.Keepthelightboxlidclosed.Openthesideflap.Lookintothelightbox.Inthetable,drawwhatyousee.
Data
Conclusion
1. CompareyourobservaCons.
2. WhywereyourobservaConsdifferent?
Observations
Lid and Flap Closed Lid Closed and Flap Open
�21
Yourteacherwilladdadividertoyourlightbox.Keeptheboxlidclosedandthesideflapopen.Drawwhatyouseeinthefollowingspace.Includeasmuchdetailasyoucan.
Conclusion1. Compareyourdrawingwithotherstudents’drawings.Howcanyouexplainthedifferences?
2. ListthecondiConsthatneedtobemetinorderforpeopletoseeanobject.Thislistshouldbeagreeduponbythewholeclass.
3. Imaginethatyoulookoutthedoorofyourscienceclassjustasafriendwalksbyandwavestoyou.Explainhowyoucanseeyourfriendinthehall.BesuretouseallofthecondiConsyoupreviouslylistedinyourexplanaCon.
�22
Reading3.3–PictureThis!
Ge`ngReadyLookcloselyatthepicture.Holdthepaperclosetoyourface.Now,setyourbookdownandlookatthepicturefromacrosstheroom.Whydothesmallpicturesyoucanseeupcloselooklikeonebigpicturefromacrosstheroom?
Inthisreading,youwilllearnhowasimilarideamakesthepicturesthatyouseeonTV.HowDoPeopleSeeObjectsaroundThem?Inclass,youlearnedaboutthingsthataffectwhatpeoplesee.Youlearnedthatthegirlintheimageyourteacherprojectedcanseethetreebecauselighttravelsfromthesun,bouncesoffthetree,andentershereye.
Inthesecondimageyourteacherprojected,somethingdifferenthappens.Lightfromthesunbouncesoffthecar,butthisCmethegirlcannotseethecar.Someofthelighttravelstowardher,butitcannotenterhereye,becausethewallblocksitspath.Ifthelightbouncingoffthecardoesnotenterhereye,thegirlcannotseethecar.DoyouthinkthegirlinImage1canseethesun?Why?(Besuretowriteaboutthepaththelightmighttake.)
DoyouthinkthegirlinImage2canseethesun?Explainyourideas.(Besuretowriteaboutthepaththelightmighttake.)
�23
InLesson2,youlookedforobjectsaroundtheroom.Youlearnedthatyoucouldonlyseesomeoftheobjectsfromyourseat.Youcouldnotseeotherobjects,eventhoughsomeofyourclassmatescouldseethem.YoualsolookedintotheendofalightboxandlearnedthatsomeCmesyoucouldseewhatwasinside,andsomeCmesyoucouldnot.YourclassusedtheseacCviCestodevelopalistofcondiConsthatneedtobemetinorderforhumanstoseeanobject.Asyouread,thinkaboutthesecondiConsandhowtheyaffectwhatyouseeonatelevision.ADifferentExperiencewithSeeing:HowDoISeeObjectsonTelevision?Ifyouhaveatelevisioninyourhome,turniton.Whatdoyouseeonthescreen?Youprobablyseeaperson,someobjects,orasceneindoorsoroutdoors.However,thereisadifferencebetweenseeingtheactualobjectandseeingtheobjectontelevision.Toseetheobject—likeachair—inreallife,youneedasourcetoprovidelight,andyouneedthelighttobounceoffthechairtoyoureye.Toseeachairontelevision,youdonotneedanaddiConalsourceoflighttobounceoffofthechair.Thetelevisionisthelightsource.Thetelevisionproduceslightthatgoesdirectlytoyoureyes.AnimageontelevisionisbothanobjectandalightsourceatthesameCme.Thatiswhyyoucanseeobjectsontelevisioneveninaroomwithnolights.LookatyouracCvitysheetfromAcCvity2.2toreviewyourlistofcondiConspeopleneedtosee.Explainwhatisdifferentaboutseeinganobjectinaroomandseeinganimageontelevision.UsethelistofcondiConsinyourexplanaCon.
Thedifferencebetweenseeinganobjectandanimageontelevisionisthatanobjectmusthavealightsourcethatisbouncinglightoffofitforustoseeit.Whenweseeanimageonthetelevision,theimageisboththeobjectandthelightsource.Pointouttostudentsthatthistrueforanylightsource;thistrueforanylightsource.Ifyoulookatalightbulb,itisboththeobjectandthelightsource.HowIsanImageonTelevisionSimilartothePictureattheBeginningofThisReading?Whenyouseeobjectsontelevision,youarereallyseeingmanyCnydots.Together,thedotscreateanimagethatlookslikesomethingreal.Thesedotsarecalledpixels.Onsometelevisions,especiallyoldones,youmaybeabletoseethepixelsifyoulookatthescreenclosely.Evenifyoucanseethepixelsupclose,theyaretoosmalltobeseenasindividualdotswhenyoustandfaraway.Instead,yourbrainwillputthemtogethertomakeanimage.ThisisthesamewaythatthepictureintheGecngReadysecConworks.Ifyoustandfarenoughaway,theCnypictureslooklikepixels,andyourbrainputsthemtogethertomakealargerimage.AnExampleofPixelsWhenyouseeanimageonyourtelevisionoronamoviescreen,youareactuallyseeingmillionsofCnydotsthatalltogetherlookliketheobjectorperson.Yourbrainputsthedotstogethersothatyouseeasingleimage.YourtelevisionscreenisacollecConofCnydotsthatjointogethertomakethebigpictureyousee.EachliLledotactslikealightsourceandanobject.Thelightmovesalongastraightpathtoyoureyes.YourbraindoesnotseeabunchofliLleobjects,becauseitputsthemtogethertoseetheimageonthetelevision.
�24
TwoMoreExamples:NewspapersandArtworkDotpaLernsarenotonlyusedfortelevisionimages.DotsarealsousedincomputerandnewspaperimagesandinpainCngs.Ifyouhaveanewspaperathome,lookatitveryclosely.Ifyouhaveamagnifyingglass,useittolookatthenewspaperupclose.CanyouseetheCnydotsthatmakeupthepicturesandthewords?WhatdoyounoCceinthephotoofaflowerandinthecloseupofthephotonexttoit?
Manythingsintheworldtodayusepixelstomakeimages.Longago,arCstsinFrancepaintedinastylecalledpoinCllism.ImagesusingpoinCllismarecreatedbypainCngmanyCnydotsorpoints.Thecolorsofthepaintarenotmixedtogetherusingabrush.Instead,thedifferentcoloreddotsareplacedveryclosetogether.WhenyoulookatthepainCngfromfaraway,thelightfromtheroombouncesoffthedotsonthepainCngandthenentersyoureye.Yourbrainblendsthedotstogethertoformalargerimage.ComparethedotsusedinpoinCllismwiththedotscreatedonatelevisionscreen.Besurethatyourcomparisondescribeswhatisalikeandwhatisdifferent.
�25
�26
Lesson4–ConstrucAngModelsofHowPeopleSeeLesson4.1–PreparingtoDevelopModels
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillconstructphysicalmodelsofhowpeoplesee.OurmodelswillrepresentthekeycomponentsandrelaConshipsthatwehavelearnedsofar.
PartA:EvaluaAngaModel
Amodelcanbegoodornot-so-good,dependingonwhatitisbeingusedfor.Whenyouuseamodeltoexplainanideatosomeone,thebestmodelisusuallyasimpleone.AgoodmodelforexplainingsomethingincludesallthekeycomponentsandtherelaConshipsbetweenthem.Itisimportantthatamodelonlyincludesthosethingsandnotextrapartsthatdonothelpexplainsomething.Itisalsoimportantthatyourmodelisaccurate.YoushouldlookcarefullyatyourmodeltobesureyouhaverepresentedthecomponentsandtherelaConshipscorrectly.Yourteachershowedyouamodeloflightusingaclaylightbulbandsometoycars.1. Howcanyouusethismodeltoexplainhowpeoplesee?
2. Howcouldyouimprovethismodeloflight?ThinkaboutthecomponentsandtherelaConshipsbetweenthem.Foreachpartofthemodel,askyourselfifyoucouldexplainhowpeopleseewithoutconsideringthatcomponent.Alsoaskyourselfifthereissomepartofseeingthatyourmodeldoesnotrepresent.
PartB:PlanYourModel
3. Amodelneedstobeconsistentwithalltheevidence.InLesson2,yougatheredevidencethatamodelofseeingneedstoincludefourkeycomponents:alightsource,anobject,aneye,andpathsbetweenthelight,theobject,andtheeye.Lookatthesuppliesyourteacherhasprovided.Whatwillyouusetorepresenteachoftheseparts?
�27
PartC:BuildandEvaluateYourModel4. Nomodelisperfect.Everymodelhasstrengthsandweaknesses.Whatarethestrengthsand
weaknessesofyourmodel?
5. Whatdidyoulearnasyoumadeyourmodelofhowpeopleseeanobject?
�28
Reading4.2–Modeling
WhyDoScienAstsUseModels?Whenyouhearthewordmodel,youmightthinkoffashionmodelsormodelairplanesormodelcars.ScienCstsusethewordmodelinaspecialway.Inscience,amodelisawaytorepresentanidea,process,orsysteminordertodescribe,explain,orpredictsomething.Modelshelptoexplainthingsthataredifficulttounderstandordifficulttoobserve.Forinstance,youcannotseeyourheart,butyoucanuseamodelofahearttoexplainhowitpumpsbloodthroughyourbody.Modelscanalsorepresentthingsthataretoobigortoosmalltoobserve.PeoplecannotobservethewholeEarthatonce,buttheycanusemapsandglobesasmodelstohelpthemexplainphenomena.Peopleontelevisionusemapstohelpthemexplainweatherorearthquakes.GlobescanhelpexplainwhyitisdayandnightatdifferentCmesindifferentpartsoftheworld.Inclass,youhavebeendevelopingamodelofhowlightmakesitpossibleforpeopletoseeobjects.Yourmodelhelpsyouunderstand,anditcanalsohelpyouexplainittootherpeople.ScienCstsusemodelstocommunicate.Asyoulearnmoreaboutlight,youmightdecidethatyouneedadifferentmodelthantheoneyoumadetoday.ScienCstsrevisetheirmodelsastheylearnnewthings.ItisOKifyourmodelofhowpeopleseegetsrevised,too.ModelshelpscienCststhinkaboutpossibleanswerstotheirquesConsaboutphenomena.YouwilluseyourmodelofseeingtoexplainhowyoucouldseethestrangeimagesinLesson1.IsItOKthatMyFriend’sModelIsDifferentfromMine?Youandyourclassmatesmayhaveconstructeddifferentmodelsofhowpeoplesee.DifferentmodelscanbehelpfulbecausetheymayshowdifferentinformaConaboutthesamephenomenon.Allmodelshaveadvantagesanddisadvantages.EvengoodmodelscanoTenbemadebeLer.Youwillbelearninghowtoevaluatemodelstodecidewhatisgoodandwhatneedstobechanged.ScienCstsevaluatetheirownmodelsandrevisethemwhennecessary.Forexample,newdatamakescienCststhinkaboutaphenomenoninanewway.Dataisawordyouwilluseoverandoveragaininscience.WhenscienCstsmakeobservaCons,theytakecarefulnoteswhiletheyareobservingsomethingwiththeirsensesormeasuringitwithinstruments.Thenotestheywriteorrecordarecalleddata.Whentheyusedatatosupportanidea,theyareusingthedataasevidence.Youwilldothesamethinginscienceclass.YourdatamaycomefromyourownobservaConsandmeasurements,oritmaycomefromatableorgraphthatsomeoneelsemade.Whenyouusedatatoexplainanidea,youareusingthedataasevidence.WhenscienCsts—oryou—developamodel,themodelneedstobeconsistentwithalltherelevantevidence.AnExampleofScienAstsRevisingTheirModelsScienCstsreviseamodelwhenitdoesnotworkverywellforexplainingsomething.Forexample,youprobablyknowthatsailorsonceexploredtheworldbysailingacrossoceans.Theydrewmapsoftheoceansandlandtoshowwhattheworldlookedlike.Thesedrawingsweresimilartotheflatmapsweusetoday.Mapsareonekindofmodelthatisdrawn.AflatmodelhelpedearlyscienCstsunderstandmostthingsabouttheworldaroundthem.However,aspeoplemadeobservaConsandtriedtoanswernewquesCons,theyfoundthataflatmodelofEarthdidnotworkforeverything.Forexample,sailorscouldseethetopsofmastsasshipsapproachedthemoverthehorizon.IfEarthwasflat,thatwouldnotmakesense.Theywouldnotseethetopsofmastsfirstandthengraduallyseetherestoftheship.TheyalsowonderedwhythesunchangesitsposiConintheskythroughouttheyear.AflatmodelofEarthwasnotconsistentwiththedatatheyobserved.
�29
ScienCstsbegantoconsideranewmodel.TheybegantousearoundmodelofEarth—likeaball.AroundEarthmodelcanexplainwhythetopsofships’mastsarevisiblefirst.AglobemodelcanexplaintheposiConsofthesuninthesky,anditcanexplainseasons.Later,photographstakenfromspaceshowedtheshapeofEarth.BeforescienCstsknewforsure,theyhadtokeeptesCngtheirmodeltoseewhetheritworkedtoexplaintheirobservaCons.Today,aglobeservesasagoodmodelformanythingsscienCstswanttoexplain.Aflatmapisgoodforshowinghowtogetfromoneplacetoanother.However,itisnotgoodforexplaininghowthesunrisesandsetsorhowashipcansailaroundtheworld.Everymodelhasadvantagesanddisadvantages.Amodelthatexplainswhatyouknowtodayabouthowlighthelpspeopleseemightnotbeagoodmodelforwhatyouwilltrytoexplainlaterintheunit.Youmightreviseyourmodelasyougathermoredata.ScienCstsrevisetheirmodels,andyoucanreviseyours,too.CheckYourUnderstandingGobacktothestatementsintheGecngReadysecCon.Nowthatyouhavefinishedreading,usethecolumnontherighttocheckwhetheryouagreeordisagreewitheachstatement.
�30
Lesson4.3–BuildingtheConsensusModel
Whatwasthepointofthelastlesson?Wewillcombinethepartsofourmodelsthatweagreeaboutintoonemodelcalledaconsensusmodel.Theconsensusmodelwillbeadiagraminsteadofaphysicalmodel.
Whatwillwedo?Wewillcombinethepartsofourmodelsthatweagreeaboutintoonemodelcalledaconsensusmodel.Theconsensusmodelwillbeadiagraminsteadofaphysicalmodel.
QuesAons:
1. Modelshaveadvantagesandtheyhavedisadvantages.Whatdidyouthinkwerethebestpartsofotherstudents’models?Why?
2. Howdoesyourdrawnmodelcomparewiththeconsensusmodelyourclasscreated?Describewhatissimilarandwhatisdifferentaboutthem.
3. Useyourclassconsensusmodeltoexplainwhyyoucannotseeyourgrandmaintheotherroom.
4. WhatdoyousCllneedtoknowabouthowlighthelpsyousee?WhatdoyousCllwanttoknowabouthowlighthelpsyousee?
�31
�32
Reading4.4–FasterthanaSpeedingBullet
Ge`ngReadyInthisreading,youwilllearnabouthowfastlightmoves.Beforeyouread,thinkofsomeofthefastestthingsyouhaveheardabout.Fillinthechartwithyourideas.
Whenpeoplesaythatturningonalightswitchlightsuptheroom,whatdotheymean?Inclass,youconstructedamodelthatshowswhatisneededforpeopletoseeobjectsinaroom.Thekeycomponentsinyourmodelwereanobject,aneye,alightsource,andthekeyrelaConshipbetweenthesewasthestraightpathsbetweenthem.Whenyouturnonalightbulb,lighttravelsfromthebulboutwardinalldirecConsandhitsobjectsintheroom.Youseetheobjectsbecauselighttravelsfromthelightbulb,bouncesofftheobjects,andthenentersyoureye.Iflighthastotravelbackandforthacrosstheroombeforeyoucanseeanobject,whydoyouseethingsinaroomassoonasyouturnonalightswitch?Theanswerhastodowiththespeedoflight.Lightisveryfast.YouwillreadabouthowscienCstsfiguredouthowfastlightis.HowDoScienAstsMeasureHowFastLightMoves?YoudonothavetowaittoseethingsaTeryouturnonalight,becauselightmovessofast.YoudonotevennoCcelightmoving.Itprobablyseemslikelightgetsfromabulbtoanobjectandbacktoyoureyeinstantly.Iflightmovessofast,howcanscienCstsmeasureit?AfamousscienCst,Galileo,triedtomeasurehowfastlightmoves.Galileowantedtomeasurethespeedoflightintheearly1600s.Todothis,hesentanassistanttothetopofahillwithalamp.HewantedtomeasurehowmuchCmeittookforlighttotravelfromonehilltoptoanother.TheassistantrecordedwhatCmeitwasonhiswatchasheturnedonhislight.Galileo,standingonanotherhill,turnedonhislightimmediatelyaTerhesawhisassistant’slight.TheassistantthenrecordedtheCmeattheinstanthesawGalileo’slight.Galileo’sideawasthattheassistantwouldhavemeasuredtheCmeittooklighttotravelfromonehilltotheotherandthenbackagain.However,thisdidnotwork.TheCmeittookGalileototurnonhislightwasactuallymuchlongerthantheCmeittookthelighttotravelfromonehilltothenext.WhenGalileofirsttriedtomeasurethespeedoflight,heandhisassistantstoodonhilltopswithlamps.Whywasitnecessaryforthemtobestandingonthetopofhillstoconducttheirexperiment?(ThinkaboutthefourcondiConsneededtoseeanobject.)
Moving Object How Fast does it go?
Fastest human runner
Fastest bicycle rider
Fastest animal
Fastest Car
Fastest man-made object
�33
Usingtheconsensusmodelyouandyourclassmatesconstructedinclass,explainhowGalileocouldseehisassistant’slight.ThiscanbedonebyshowinghowthekeycomponentsinthemodelrepresentwhatwasinvolvedinGalileoseeinghisassistant’slight.
WhatDoWeKnowabouttheSpeedofLightToday?Inhisexperiment,Galileoandhisassistantwereseveralmilesapart.Today,humanscansendobjectsmuchfartheraway.In1969,theUnitedStatessentastronautstothemoon.Themoonisabout240,000miles(365,000km)awayfromEarth.ThisisliketravelingaroundthewholeEarth10Cmes.Thinkabouthowlongitwouldtakeyoutodrivearoundtheearthinacar.Duringthemissiontothemoon,scienCstsnoCcedthatittookaboutonesecondforlightfromEarthtoreachtheastronautsonthemoon.LightcantravelaroundEarth10Cmesinjustonesecond.Nothingelsecantravelthatfast.Thesunismuchfartherawaythanthemoon.Travelingtothesunwouldbeliketaking37,000tripsaroundEarth.EventhoughEarthisahugedistancefromthesun,itonlytakeslightfromthesunabouteightminutestogettoEarth.Thismeansthatwhenyouseethesun,youareseeinghowitlookedeightminutesago.HowDoestheSpeedofLightComparetoOtherFastThings?Inthebeginningofthisreading,youthoughtaboutsomefastthings.Theworld’sfastestpeoplecanrunatabout25milesperhour.Acheetahcanrun70milesperhour.Thefastestanimalistheperegrinefalcon.Itcanflyover200milesperhour.Humanshavemademachinesthatcanmoveextremelyfast.Thefastestapersonhasevermadeabicyclegois167milesperhour.AThrustSSC,theworld’sfastestcar,cango760milesperhour.Thefastesthuman-madeobjectstravelinspace.AspacecraTcalledtheHeliostraveledat150,000milesperhour(or241,400kmperhour).Atthisspeed,itwouldtakeaboutamonthtotravelfromEarthtothesun.Itonlytakeslighteightminutestotravelfromthesuntotheearthbecauselightmovesmuchfasterthananythinghumanshaveevermade.Lightmovesthroughspaceat670,000,000milesperhour.Thismeansthatitwouldtakeajetairplane25daystotravelthesamedistancethatlightcantravelinonesecond.Whenyoufliponalightswitch,itseemsthatlighthitsyoureyeinstantlybecauselightmovessofast.ItmovesbackandforthacrosstheroomsofastthatyoudonotevennoCceitmoving.HowCantheSpeedofLightHelpPeopleMoveFaster?OnewaythatthespeedoflightmaLerstoscienCstsiswhentheythinkaboutspacetravel.Rightnow,ifpeoplecouldtraveltoMarswiththespaceshuLle,itwouldtakeninemonthstogettoMars.ItwouldtakeanotherninemonthstogetbacktoEarth.ScienCstsatNASAarestudyinghowtousenewspaceshipscalledsolarsails.Thisisaphotoofasolarsail.TheseshipscouldtravelthousandsofCmesfasterthanthespaceshuLle.ThespaceshuLleispushedbyburningrocketfuel,butsolarsailsarepushedbylight.Thatmeanstheywouldbemuchfaster.ExperimenCngwithsolarsailsisoneofthewaysthatscienCstsusetheirunderstandingoflighttocreatesomethingnew.Asyouhavelearned,lightmovesextremelyfast,anditwillbeabletohelppeopledothingsevenfaster.InLesson4,youwilllearnaboutwhathappenstothelightthatentersyoureye.
�34
Lesson5–TheEyeasaLightSensorLesson5.1–HowtheEyeWorks
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewilllearnabouthowoureyesactlikealightsensor.
ProcedureYourteacherwillprojectarepresentaConoftheeye.Usethefollowingspacetodraworwritenotesaboutwhatyourteacherreviewsinclass.
Youaregoingtogoonahuntusingalightsensor.Thesensoronlydetectslightthatcomesfromobjectsdirectlyinfrontofit.Thelighthastobounceofftheobjectorcomefromalightsourceandtravelstraightintothesensor.Inthedrawings,whereisthelightthatthelightsensordetectscomingfrom?Explain.DrawlinesandarrowsinthedrawingstoshowthepaththelighttravelsunClitentersthelightsensor.
Usethelightsensortomeasurelightindifferentplacesintheroom.RecordthelocaCon,the
�35
Usethelightsensortomeasurelightindifferentplacesintheroom.RecordthelocaCon,themeasurement,andtheunitsinthefollowingtable.
Wherearethebrightestpartsoftheroom?Whatrangeofvaluesisshownonthedatalogger?
Wherearetheleastbrightpartsoftheroom?Whatrangeofvaluesisshownonthedatalogger?
Conclusion
1. Likethelightsensor,theeyeactsasasensoroflight.Lighthastocomeintothelightsensorandintoyoureyefromoutside.Howdoestheconsensusmodeloflighthelptoexplainwhichpartsoftheroomarethebrightest(ortheleastbright)totheeyes?
2. Ifnolightiscomingfromanyobjectintoyoureye,thenwhatwillyousee?WhatevidencefromaclassroomacCvitysupportsyouranswer?
Location Light Measurement
�36
3.Doesalightsensordetectanobject,ordoesitdetectthelightcomingfromanobject?Howdoesthiscomparewithhowtheeyeworks?
4.WhydoesitmakeadifferenceinwhichdirecConyoupointthelightsensor?
5.WhydoesitmakeadifferencehowfarawaythelightsensorisfromtheobjectatwhichitispoinCng?
�37
�38
Lesson5.2–ExploringShadows
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillexploreshadowsinourworld.
ProcedureIfitisasunnyday,gooutsideandlookforashadow.Inthefollowingspace,drawwherethelightsourceiscomparedtotheshadowandtheobjectthatmadetheshadow.Ifpossible,observetheshadowagainanhourlater.Comparethesize,shape,andposiConofthetwoshadows.YoucouldalsodothisacCvityusingashadowinside.
�39
�40
Reading5.3–EyesintheAnimalKingdom
Ge`ngReadyTrythisathome.Gointoasmallroomwithamirror,likeabathroom.Lookcloselyinthemirroratyoureyes;thenturnoffthelightandmaketheroomasdarkaspossible.Ifyoucannotmaketheroomdark,shutyoureyesandcoverthemwithyourhands.Waitforseveralseconds,andthenturnthelightsonasyouconCnuetolookatyoureyesinthemirror.WhatchangesdoyounoCceinyoureyesimmediatelyaTeryouturnthelighton?Whydoyouthinkthischangehappens?
Doyouthinkthesamechangehappenstoanimals’eyes?Inthisreading,youwilllearnwhyyoureyeslookdifferentdependingonwhetherthelightsareonoroff.Youwillalsolearnwhetheranimals’eyesdosomethingsimilarordifferent.HowDoMyEyesSenseLight?Inclass,youlearnedhowthehumaneyeworksasalightsensor.Whenyouseeanobjectinaroom,thelightisbouncingoffofthatobjectandgoingstraightintoyoureye.Howdoesyoureyehelpyousee?Theeyehasseveralimportantparts.Theopeninginthecenteriscalledthepupil.Inthepicture,thepupilislabeled.Itlooksblack,butitisreallyjustlikeaclearwindowthatletslightintotheeye.ThecorneaisaprotecCvecoveringoverthewholeeye.Itkeepstheeyefromgecngscratched.Thelensintheeyeislikethelensineyeglassesorinacamera.Thelensfocusesthelightcomingintotheeye.ThelensfocuseslightontothebackoftheeyeballonanareacalledthereCna.SensorsinthereCnadetectthelightthatreachesthem.ThosesensorssendasignaltothebrainthroughtheopCcnerve.HowDothePartsoftheEyeWorkTogether?Whenyouseealightbulb,severalthingshappen.First,someofthelightcomingfromthebulbentersyoureyeandreachesyourreCna.Second,yourreCnasendsasignaltoyourbrain.Third,yourbrainrecognizesthatthesignalisalightfromalightbulb.Lookatthediagram.Ifacoffeemugwereintheroomsothatyoucouldseeit,thensomeofthelightfromthelightbulbwouldbebouncingoffofthemug.SomeofthelightbouncingoffofthemugwouldenteryoureyeandreachthereCna.Asignalwouldgotoyourbrain,andrecognizeitastheimageofamug.Alothastohappenforyoutoseesomething;butithappensveryquickly.
�41
UsingEquipmentasaLightSensorYoureyeisasensor.Specialequipmentalsocanactasasensor.Thelightsensorsthatyouusedinthislessonareoneexample.Whenyoupointedthesensoratanobject,itdetectedthelightcomingfromthatobject.Justlikewithyoureyesorwithcameras,lighthadtoenterthesensorinordertobedetected.Insteadofsendingasignalthatyourbrainrecognizesasanimage,thelightsensorsendsasignaltoasmallcomputer.Thiscomputerreceivesthesignalanddisplaysanumberthattellshowmuchlightisenteringthesensor.Whenyousawanobjectintheroomthatlookedbrighttoyoureyes,thelightsensorshowedaveryhighnumberonitsdisplay.YoumayhavegoLenahighnumberwhenyoupointedthesensoratthelightsoratawindow.Whenyousawanobjectthatlookeddimtoyoureyes,thesensorshowedalownumberonitsdisplay.YoumayhavegoLenlownumberswhenyoupointedthesensorundertablesordesks.Whenlightentersasensor,acomputergivesinformaCon.Whenlightentersyoureye,yourbraingivesyouinformaCon.DoAnimalEyesWorklikeHumanEyes?Justlikehumaneyes,animals’eyesworkbydetecCnglight.However,therearesomedifferencesbetweenhumaneyesandsomeanimals’eyes.Inthisreading,youwilllearnaboutthreeanimalsthathaveeyeswithspecialcharacterisCcs.
�42
PolarBearsHaveyoueverplayedoutsideinthesnowonasunnydayorplayedonawhitesandbeachonasunnyday?Ifyouhave,youknowhowbrightitiswhenthesun’slightbouncesoffofthewhitesnoworthewhitesand.YoualsomayhavenoCcedthatitisdifficulttoseeinbrightlightwithoutsquinCng.Whydopeoplesquint?Peoplesquintsothattheireyelidssqueezetogetherandcoverpartoftheiris.WhentheirisisparCallycovered,thepathofsomeofthelightgoingintotheeyesgetsblocked.Polarbearsliveoutsideinthesnow.Becausepolarbearshavetohuntforfoodinintensesunlight,theireyeshavetoallowthemtoseeinverybrightlight.PolarbeareyeshaveaprotecCve,clearcoverovertheireyeballs.Thebearscanseethroughthiscoveringtohunt.Thecoveringprotectstheireyesfrombrightsunlightandthelightthatbouncesoffthesnow.Itiskindoflikehavingbuilt-insunglasses.ThisprotecCvecoveralsohelpsprotectabear’seyeswhenitswimsunderwater.CatsCatsalsohaveeyesadaptedtotheirenvironment.Asnaturalhunters,catsneedtohavekeensensesinordertostalktheirprey.CatscanseealmostaswellashumansduringthedayCme,buttheirnighcmevisionismuchbeLer.Althoughcatscannotseeincompletedarkness,theycanseemuchbeLerthanhumansinenvironmentsthatappeardarktous.Infact,catscanseesixCmesbeLerthanhumansinplaceswithlowlight.Thereareseveralreasonsforthis.CatreCnasaremoresensiCvethanhumanreCnas.Duringtheday,acat’spupillookslikeaslit.Thisslitdecreasestheamountoflightenteringtheeyesandpreventsthecatfromhavingtosquint.Aroundpupil,likeinahumaneye,wouldletintoomuchlight.Atnight,orwhencatsareindarkplaces,theirpupilscanopenthreeCmeswiderthanthoseofhumans.Thewideropeningletsinmuchmorelight.Likepolarbears,theyhaveatransparentprotecCvecoverovertheireyesthatallowthemtoseewellinbrightdaylight.Youmayhaveseenacat’seyesappeartoglowinthedarkwhenlightisshinedonthem,asinthephoto.Thetransparentcovercausescats’eyestoappeartoglowatnight.YoumayhavealsonoCcedthisondogs.GiantSeaSquidThisisaphotoofasquid.Giantseasquidsareknowntohavethelargesteyesofanyanimalintheanimalkingdom.Eventhoughmanyanimalsarelargerthantheseasquid,nonehavesuchbigeyes.Somegiantseasquidshaveeyesaboutthesizeofyourhead.Theirhugeeyeshaveverylargepupilsthatletinasmuchlightaspossible.Sodeepinthesea,whereitisverydark,theireyescanletintheliLlebitoflightthatreachesthem.Evensquidsandcats,whichcanseeinverydarkplaces,needsomelighttosee.Evenwithlargepupils,ifnolightenterstheeye,thentheanimalwillnotbeabletosee.
�43
SummarizingAnimportantskillinanysubjectissummarizing.Whenyousummarizesomethingyouhaveread,youtellthemainideas.Thatmeansthinkingaboutwhatseemstobethemostimportantideasinwhatyouread.Inthefollowingspace,summarizewhatyouhavelearnedaboutanimaleyesintoday’sreading.(Thinkaboutwheretheyliveandwhattheireyeseyesneedtobeabletodofortheanimaltosurviveinitsenvironment.)ThebeginningofasummaryiswriLenforyoutogetyoustarted.Differentanimals’eyesworkindifferentways.Howtheireyesworkdependsonthefollowingfactors:
Showyourunderstandingbyfillingintheblanksinthefollowingsentences.Inbrightlights,thepupilsofahuman’seyes_____________________.Indarkness,thepupilsofahuman’seyes________________________.
Explainwhythefollowingsentenceisnotcorrect:Becausecatshavesuchgoodeyes,theycanseewhenitiscompletelydark.
�44
Lesson6–HowAreShadowsCreated?Lesson6.1–IntroducingShadows
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillexploreshadowsanduseourlightmodeltoexplainourobservaCons.
ProcedureTheteacherwilldimthelightsintheclassroom.Putapieceofwhitepaperonyourdesk.Useyourhand(oranobject)andaflashlighttocreateashadowonthepaper.ExplorewhathappenstotheshadowinthreecondiCons:
movingthehandorobjectmovingtheflashlightmovingthepaper
RecordyourobservaConsinthedatatable.DiscussthefollowingquesConswithyourgroup:Howdoestheshapeoftheshadowcomparetotheshapeoftheobject?Howcanyouchangethesizeoftheshadow?HowcanyouchangethelocaConoftheshadow?
Data
Conditions Observation
Moving the Object
Moving the Flashlight
Moving the Paper
�45
Conclusion
1. Whatpartsofthelightmodeldoyouneedtoexplainhowyouseeashadow?
2. Howdoesthelightmodelhelpyouexplainthattheshapeoftheshadowisliketheshapeoftheobject?
3. HowdoesthelightmodelhelpyouexplainhowyoucanchangethelocaConoftheshadow?
4. Howdoesseeinganobjectcomparewithseeingashadow?
�46
Reading6.2–AMidnightCrime
Ge`ngReadyReadastoryaboutacrimethattookplaceonadarknight.WewillusewhatwehavelearnedaboutlightandshadowstoanswerquesConsandsolvethecrime.AMidnightCrimeHalloweenwasperfect,withaclearanddarksky.ManypeoplecametotheSmiths’Halloweenparty.EveryonehadagreatCme,andsomepeoplestayedunCldawn.ATereveryoneleT,theSmithsdiscoveredthatsomeexpensivejewelrywasmissing.Theycalledthepolice.ThepoliceaskedeveryonewhohadbeenatthepartytoanswerafewquesCons.Apoliceofficerlistenedcarefullytoeachperson’sstory.Mr.Jonessaid,“IleTtheSmiths’partyaroundmidnight,andIwalkedtomycar.Itwascold,buttheskywasclearwithnoclouds.Itwastotallydarkoutside.WhenIgotinmycartoleave,Isawsomeonewalkingoutofthehouseholdingadecoratedwoodenbox.Iturnedonthecarlights,andthepersonimmediatelyturnedaroundandwalkedawayfromme.Heorshewalkeddirectlytowardthewallnexttothehouse.IcouldseetheshadowonthewallgecnglargerandlargerunClthepersondisappearedaroundthecorner.AtthatCme,Ididnotsuspectanything,soIjustdroveaway.”Thepoliceofficerthoughtforaminuteandsaid,“YouareunderarrestonsuspicionofstealingtheSmiths’jewelry.Yourstatementincludestoomanyimpossibledetails.IsuspectyouknowsomethingaboutthedisappearanceofthejewelrycollecCon.”FollowUpQuesAons1. WhataretheimpossibledetailsinMr.Jones’sstatementtothepolice?Explainwhythesedetails
areimpossible.
2. ConstructadrawnmodelthathelpsexplainhowMr.Joneswouldhavereallyseenaperson’sshadow.
Detail in the Statement Why is That Impossible?
�47
3.IfMr.Joneshadnotturnedonhiscarlights,wouldhehavebeenabletoseetheperson?Wouldhehavebeenabletoseetheperson’sshadow?Explain.
4.Explainwhylightisnecessarytoseeanobject.
�48
Lesson6.3–ConnecAngShadowstotheLightModel
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillusethelightmodeltoexplainhowshadowsarecreatedandhowweseeshadows.
ProcedureLookatthediagram.Thediagramshowstheconsensusmodelwithanewcomponentadded.Behindtheobject(thetriangle)isasurface.Thesurfacecouldbeapieceofpaper,awall,orthetopofyourdesk.Thetrianglerepresentsanyobjectthatcouldmakeashadowonthesurface.Constructadrawnmodelofhowshadowsarecreatedandhowyouseeshadows.Drawtheshadowoftheobjectonthescreen.Addlinesandarrowstoyourdrawingtoshowhowtheshadowiscreatedandhowtheeyeseestheshadow.MakesureyourdrawingincludesallthecomponentsofthelightmodelthatrepresentthecondiConsnecessarytoseeanobject.
Conclusion
1. DescribeyourmodelinafewsentencessothatyoucouldpresentyourexplanaContotheclass.
2. UseyourmodeltoanswerthefollowingquesCons.
a. Whatissimilarbetweenseeinganobjectandseeingashadow?
b. Whatisdifferentbetweenseeinganobjectandseeingashadow?
c. Modelscanbeusefulnotonlytounderstandandexplainbutalsotopredictsomethingbeforeexperiencingit.Usingyourmodel,predictwhatalightdetectorwoulddetectwhenpoinCngtowardtheshadowedareaonthescreen.Explain.
�49
Reading6.4–AllShadowsAreNottheSame
Ge`ngReadyHaveyoueverbeenoutsideonasunnydayandwatchedyourshadow?Maybeyoudancedinfrontofawalltowatchhowyourshadowmoves.Maybeyouwatchedyourshadowchangeasyougotclosertoabuilding.Inthisreading,youaregoingtodoafewsimpleacCviCestolearnmoreaboutshadows.Allyouwillneedislightandyourownhand.AsyoudotheacCviCes,trytothinkaboutwhatishappeningandwhy.Youmightbeabletofigureoutsomethingsevenbeforeyoureadaboutthem.TryThisatHomeGointoaroomwithalotoflightsandwindows.Turnonallthelights,andholdyourhandaboutsixinchesaboveatableorthefloor.Trythisduringthedayifyoucan.Lookattheedgesofyourhand’sshadow.Aretheyblurryoraretheyclearandstraight?Now,gointoaroomwithnowindowswhereyoucanturnallthelightsoffbutonelightontheceiling.Thisshouldbeasmalllight,notalongfluorescentlight.Iftheroomonlyhasadeskortablelamp,youcanuseoneofthoseinstead.Holdyourhandsixinchesabovethetableorflooragain.
Howdoesthisshadowcomparetotheshadowyoumadebeforewithlotsoflights?Makesuretodescribehowbothshadowsarethesameanddifferent,payingspecialaLenContotheedgesoftheshadows.
Whathappenstotheblurrinessoftheshadowifyoumoveyourhandcloserandfartherfromthelight?Whathappenstotheshadow’ssize?
YouprobablynoCcedthatyourshadowwasfuzzywhenthereweremanylightson.Yourshadowwas
�50
YouprobablynoCcedthatyourshadowwasfuzzywhenthereweremanylightson.Yourshadowwaslessblurrywhentherewasonlyonelighton.Inthisreading,youwilllearnhowthelightmodelcanhelpyouexplainwhytheedgesoftheshadowofyoursamehandlooksclearsomeCmesandblurrysomeCmes.
HowDoIMakeaClearShadow?Beforeyoulearnwhatmakesafuzzyshadow,youshouldunderstandwhysomeshadowshaveclearedges.IntheGecngReadyacCvity,yousawthatyourhandhadaclearshadowwhentherewasonlyonelighton.Inclass,youusedalightmodeltoexplainhowashadowisformedwhenasinglelightsourceshinesonanobject.Youmayhavedrawnsomethingsimilartothefollowingexample.Lightleavingalightsourcetravelsinstraightlines.Ifahandblocksthepathbetweenthelightsourceandthetable,thenashadowwillbeformedbehindthehand.Why?Lightthathitsthehandwillnotgettothetable.Lightthatmissesthehandwillgettothetable.Wheneveryplaceonthetableeitherreceiveslightordoesnotreceivelight,theshadowhasclearedges.Thereisaclearborderbetweenthelitandunlitareas(theshadow)onthetable.Lookatthepreviousdiagram.NoCcehowthediagramrepresentsthelightsource,yourhand,andtheshadowonthetable.
�51
HowCanIMakeaFuzzyShadow?IntheGecngReadyacCvity,younoCcedthatturningonmorethanonelightsourcecausedtheshadowofyourhandtobefuzzy.Itmighthavecausedtheshadowstolookliketheyoverlap.Youcanunderstandwhythishappensbydrawingthelightmodelwithtwolightsources.Thefollowingdrawingshowsthelightmodelwithtwolights.ItlookslikeonlyLightSource#1isshiningonthehandinthediagram.NolightiscomingfromLightSource#2inthefollowingdiagram.
IfonlyLightSource#1isturnedon,therewillbeaclearshadowonthetableorfloor.However,somethingdifferenthappenswhenyouturnonLightSource#2atthesameCme.Lookcloselyatthefollowingtoseehowtheshadowchanges.ThefollowingdiagramshowslightfromLightSource#1asdoLedlinesandlightfromLightSource#2assolidlines.
�52
Thisdrawingwillmakemoresenseifyouthinkabouteachpartofthedrawingandaboutwhatyoudid.ThetableisrepresentedbythelineacrosstheboLomofthedrawing,butthelightsarehicngyourhandfromdifferentdirecCons.Canyouseethatthedarkpartoftheshadowwouldbethepartinthemiddleofyourhand?Nolightfromeitherlightsourcegetsthroughyourhandtoreachthisarea.Theshadowthereisdark,butnexttoitareareasthatarelitbylightfromonlyoneofthelightsources,becauseyourhandblocksthelightfromtheotherlightsource.Theseareasarelessdark,buttheyarenotbright.Theseareasarethepartsoftheshadowthataregrayorblurry.AnotherExampleThephotoshowstheshadowformedwhentwolightsourcesshineonaballonasCck.NoCcethatthereisaverydarkpartoftheshadowwherenolightfromeitherlightsourcereachesthewall.NoCcethattherearetwolessdark(orgray)areaswherelightfromonlyonesourcereachesthewall.Whentherearetwolightsources,ashadowhasdarkerandlighterareas.Thedarkareaiswherenolightfromeithersourcereachesthewall.Theareasthatarenotasdarkareformedwherelightfromonlyonesourcereachesthewall.ComparingShadows:OneLightSourceComparedtoTwoLightSourcesShadowsareformedwhenanobjectblockslightfromreachingsomething.Youusedyourhandtoblockthepathbetweenthelightandthewallortable.ThepictureshowsaballonasCckblockingthepathbetweenthelightsandthewall.Whenthereisonlyonelightsource,thereisaclearborderbetweenthedarkareaandthelightareaonthewall.Whentherearetwolightsources,thedarkareaoftheshadowissurroundedbyareasthatarenotasdark.Theselessdarkareasmaketheedgesofshadowslookfuzzybecausetheypreventaclearborderbetweentheverydarkandvery
�53
lightpartsofthewall.Themorelightsourcesthereare,thefuzziertheedgesoftheshadowwilllook.WhydoyouthinkthesCckthatisholdingtheballismakingtwoshadows?Whydoyouthinkthattheyarebothgrayinsteadofdark?
Whenyouturnedonmanylightsintheroomandlookedatyourhand’sshadow,whywasthemiddlepartoftheshadowdarkandtheareasclosertotheedgelessdark?
CanaShadowBeFuzzywithOnlyOneLight?YoumayhavenoCcedthatyoucouldmaketheshadowofyourhandlookfuzzywithonlyonelightturnedon.Thiscanhappenifyourhandisclosetothelightorifthelightsourceislargeandclosetotheobject.Thelightmodelcanhelpyouunderstandwhythishappens,too.Thenextdrawingshowshowashadowisformedusingalargerlightsource.LightcomingfromtheleTsideofthesourceisshownwithdoLedlines,andlightfromtherightsideofthesourceisshownwithsolidlines.Insteadofallthelightcomingfromoneplaceinthelightsource,lightcomesfromeverywhereinthelightsource.Thisisjustlikehavingseveralseparatelightsources,someatthetopandsomeattheboLom.LighterareasareformedwhenlightfromonlythetoportheboLomofthesourcecanreachthewall.Adarkareaoftheshadowappearswherenolightfromanywhereinthesourcereachesthewall.Becausethelightfromlargersourcesleavesfromdifferentplaces,theyusuallyformfuzzyshadows.
�54
WhenCanYouSeeShadowslikeThisinOtherPlaces?Haveyoueverseenafluorescent(floor-eh-sent)lightbulb?Theyareshapedlikelongtubes.Youmayhavethemintheceilingofyourclassroomsatschool.Shadowsformedbyfluorescentlightbulbswillalmostalwaysbefuzzybecausetheyarealargelightsource.CheckthenextCmeyouareinschoolbyholdingyourhandaboveyourdesk.YouhaveprobablynoCcedthisfuzzinessaroundshadowsbefore.Themodelthatyouhavedevelopedthroughthefirstfivelessonsallowsyoutoexplainwhythishappens.ModelsareverypowerfultoolsthatscienCstsusetohelpthemexplaintheworldaroundthem.Nowyouareusingthem,too.
�55
Reading6.5–StarsandtheSolarSystem
Ge`ngReadyLookatthisphotograph.Whatdoyouthinkisthepicture?Youmightbesurprisedtolearnthatthisisaphotographofgalaxies.Eachgalaxyismadeupofbillionsofstars.Infact,theuniversehasmorethan100billiongalaxies,andeachgalaxyhasabout100billionstars.Sotherearealotofstars.PeoplecanseeonlyaverysmallnumberofthemfromEarth.StarryNightOursunisahugeballoffirethatradiateslight.Starsarealsohugeballsoffirethatradiatelight,buttheyaremuch,muchfartheraway,whichiswhytheyseemsmaller.Likeoursun,starsshinelightinalldirecCons.SomeofthelighttravelsinthedirecConofEarth.Eventhoughlighttravelsveryfast,moststarsaresofarawaythatittakesmillionsofyearsfortheirlighttoreachEarth.So,whenyouseeastar,youcanseelightthatwasproducedmillionsofyearsago.Thismeansthatwhenyoulookatthestarrynightsky,youactuallylookintothepast.BytheCmelightreachesyou,thestarsthatproduceditmayhaveexplodedorcooleddownanddied.Itmakessensetoassumethatsomeofthestarsyouseedonotexistanymore.Planets,ontheotherhand,donotgeneratelight.YouseeplanetsbecausetheyarerelaCvelyclosetothesun,andtheyarelitbythesun.Lighttravelsfromthesuntotheplanetsandthenbouncesoffofthem.SomeofthislighttravelstoyoureyeshereonEarth.Usewhatyouhavelearnedaboutlightandsighttodrawoneormoremodelsthatexplain1. howyouseestars.
2. howyouseeplanets.
3. whyyoucannotseethestarsorplanetsonacloudynight.
TheSolarSystemTheuniversecontainsbillionsofgalaxies,butmostofthestarsyouseeintheskybelongtotheMilkyWaygalaxy.TheMilkyWaygalaxyconsistsofhundredsofbillionsofstars,oneofwhichisEarth’ssun.Peoplecallit“thesun,”asthoughthereisonlyone.Buttheuniversecontainsmanyothersuns,too.
�56
TheEarth’ssunisnotatthecenteroftheMilkyWay,likeitsomeCmesseemstobeinpictures.Thesunisactuallyofftooneside.Eightplanets,theirmoons,andotherobjectssuchasasteroidsandcomets,movearoundtheEarth’ssun.Alltheseobjectstogetherarecalledthesolarsystem.ThesunisthebiggestobjectinEarth’ssolarsystem.Itmakesupmorethan99%ofthesolarsystem’stotalmass.Alltheotherobjectsinthesolarsystemarearrangedaroundthesun.Theobjectsareconstantlymovinginorbitsaroundthesun.
Lookatthemodelofthesolarsystem.ItshowstheposiConoftheplanetsinrelaContothesunandcomparedtoeachother.Italsoshowstheshapeofthepatheachplanetmakesaroundthesun.Thesepathsarecalledorbits.Likeallmodels,thismodelhaslimitaCons.TherelaCvesizesoftheobjectsinthemodelarenotaccurate.Forexample,inthismodel,thesunseemsabout50Cmesbiggerthantheearth,butitisactuallymorethan300,000CmeslargerthanEarth.Torepresentthesunandtheplanets’sizesaccurately,amodelofthesolarsystemwouldhavetobebiggerthanyourschool.Whatelseisnotrepresentedaccuratelyinthemodel?
�57
DoAllScienAstsAgreeonThisModeloftheSolarSystem?ScienCstsusedtothinktherewerenineplanetsinthesolarsystem—theeightthatareinthediagramandPluto.Afewyearsago,scienCstsdecidedthatPlutowasnotaplanet.Why?ScienCstsbelievethatalltheplanetsinthesolarsystemoriginatedfromahugecloudofgasanddustthatusedtosurroundthesun.Forthisreason,alltheplanetshavemanythingsincommon.Theshapeoftheirorbitsisonethingtheyhaveincommon.However,Pluto’sorbitisverydifferentfromtheotherplanets’orbits.Infact,itsorbitcrossesNeptune’s,soatCmesitisfartherawayfromthesunthanNeptune,andatotherCmesitiscloser.AsscienCstscollectnewevidence,theysomeCmesrealizethatwhattheythoughtbeforewaswrong.Theychangetheirideasandtheychangetheirmodels.Thisisanexampleofhowscienceworks.Ifyoulookaroundatmodelsofthesolarsystem,youmightseesomewithnineplanetsandsomewitheightplanets.SomedayscienCstsmaygathernewevidencethatwillconvincethemthattheyneedtochangetheirmodelofthesolarsystemagain.HowDoesLightAffectWhatISeeintheSky?Whenyoulookattheskyduringtheday,youcanseethesunandsomeCmesthemoon,butyouneverseetheplanetsorthestars.Thisisbecausethesun’slightissobrightthatyoureyescannotdetectmuchweakerlighteventhoughtheweakerlightalsoreachesyoureyes.Itislikegoingsomeplacewherethemusicisloudoracrowdischeeringreallyloudly,andyoucannothearwhatyourfriendnexttoyouissaying.Normallyyoucouldhearyourfriend,buttheloudnoisemakeseveryothersoundseemquiet.Thebrightlightofthesunmakesthelightfromtheplanetsandthestarstooweakforyoutodetect.
�58
Lesson7–ScaBeringandReflecAonofLightLesson7.1–ReflecAon
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillinvesCgatewhathappenswhenlightstrikesamirrorandbouncesoffofit.
PredicAon:
WhatdoyouthinkwillhappentothelightwhenyoushineitonamirrorfromdifferentdirecCons?
ProcedurePlacetheAnglessheetsothatthethickhorizontallineisalongawallorthesideofabox.Tapethepaperdown,soitcannotmove.ALachaflashlighttoarulerorametersCck,sothattheflashlightlensisabout30cmfromtheAnglessheet.Iftheflashlightcanbefocused,thenfocusthebeam,soitisasnarrowaspossible.Besuretheflashlightpointsstraightdowntheruler,andtheflashlightsitsflatonthetable.ALachalightsensortoadifferentrulerormetersCck,sothatthedetectorendofthesensorisabout30cmfromtheAnglessheets.Besurethesensorpointsstraightdowntherulerandsitsflat.Theflashlightbeamshouldhitthewall(orbox)directlyabovethedoLedcenterlineontheAnglessheet.UsetapetoaLachaflatmirrortotheverCcalsurface.Besurethemirroriscompletelyflatagainstthewall.PlacetherulerandflashlightsothelightshinesdirectlyatthemirrorjustabovethedarkhorizontallineonthebaseoftheAnglessheet.PosiContheruleralongLine1totherightofthedoLedcenterlineontheAnglessheet.OntheleTsideofthedoLedcenterline,movetherulerwiththelightsensoraroundthepointonthepaperwhereallthelinesmeet.MovethesensorinthiswayunClyoufindtheposiConthatgivesthehighestlightreading.Inthedatatable,intherowforPosiCon1,drawtheplacementofthelightsensorthatgaveyouthelargestreading.Recordthenumberofthelinethatthelightsensorison.WriteanyobservaConsyoumayhavemadeasyoufoundthebiggestvalue.RepeatSteps1–3fourCmes,eachCmeplacingtheflashlightonadifferentlinetotherightofthedoLedlineandkeepingitinthatplacebutmovingthelightsensoronLines1through5totheleTofthedoLedcenterline.
�59
�60
Conclusion
1. WhatpaLernsdoyounoCceinthedrawingsyoumadeinyourtable?
2. Thefollowingmodelshowslightraysastheyleaveasource.Someofthelightrayswillhitthemirror.BasedonwhatyoulearnedinthisacCvityabouthowlightbouncesoffofamirror,usearulertodrawthepatheachlightraywilltakeaTeritbouncesoffthemirror.
�61
�62
Lesson7.2–InvesAgaAngScaBeringandReflecAon
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillusealightsensortoinvesCgatewherelightgoesaTeritbouncesoffoftwodifferentsurfaces.ThisinvesCgaConwillhelpexplainwhyamirrorlooksdifferentfromasheetofpaper,eventhoughlightbouncesoffofboth.
PredicAon:
TodothisacCvity,usethesamesetupthatyouusedinAcCvity6.1.1. InAcCvity6.1youinvesCgatedhowlightbehavedwhenitbouncedoffamirror.Howdidthelight
sensor’sreadingschangeasyoushinedthelightonthemirrorandthenmovedthesensorfromPosiCon1through5?
2. Basedonthelightmodel,whatdoyouthinkthelightsensorreadingswillshowasyoumovethesensorfromPosiCon1throughPosiCon5whenyoushinetheflashlightonasheetofpaper?
ProcedurePreparethesetupwiththeflashlight,lightsensor,mirror,andtworulersormetersCcksjustlikeinAcCvity6.1.UsetheAnglesheetagain,asinStep1ofthatacCvity.PlacethemetersCckwiththeflashlightalongPosiCon3totherightofthedoLedcenterlineontheAnglessheet.TapethismetersCcktothetablesothatitdoesnotmoveduringthisacCvity.PosiConthemetersCckwiththesensoratPosiCon1ontheleTsideofthedoLedcenterline.Recordthemeasurementfromthelightsensorinthedatatable.MovethelightsensorthrougheachposiCon(1–5)ontheAnglessheet,andrecordeachmeasurementinthedatatable.ATeryoucompletethedatatable,removethemirrorandreplaceitwithapieceofwhitepaper.Createanewdatatablejustliketheoneyouusedforlightbouncingoffthemirror.TitlethenewdatatableLightBouncingOffofPaper.RepeatSteps1–3withthelightshiningonthesheetofpaper.RecordeachmeasurementfromPosiCons1–5inyournewdatatable.
�63
Data
Recordthedatayoucollectabouthowlightbouncesoffofamirror.
Conclusion
1. Comparethedatayoucollectedforthemirrorwiththedatayoucollectedforthesheetofpaper.
2. HowdoyourdatacomparewithyourpredicCons?Iftheyarenotthesame,describehowyourpredicConwasdifferentfromwhatyouactuallymeasured.
3. Whatisdifferentaboutthemirrorandthepaperthatcouldexplainwhytheresultsweredifferentforeachobject?
Sensor Position Mirror Sensor Reading
White Paper Sensor Reading
1
2
3
4
5
�64
Lesson7.3–ScaBeringandReflecAngPart1
Whatwasthepointofthelastlesson?
Imaginethatyoushineaflashlightontoamirror,asshowninthefollowingimage.Drawtwodifferentplaceswhereapersoncouldstandsothatlightbouncingoffofthemirrorwillreachthem.Addraystothemodel
Conclusion
1. Explainwhythepersoncouldstandineitheroftheseplaces.
�65
2.Imaginethatyoushineaflashlightontoabrickwall,asshowninthefollowingimage.Drawtwodifferentplaceswhereapersoncouldstandsothatlightbouncingoffofthewallwillreachthem.
3.Explainwhythepersoncouldstandinbothoftheseplaces.Addraystothemodel.
�66
Lesson7.4–ExplainingScaBering,ReflecAngandImages
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewilluseourlightmodeltoexplainwhywecanseeanimageofourselvesinamirrorbutwecannotseeourselvesinasheetofpaperorwood.
ProcedureThefollowingdiagramshowswhatyouseewhenyourteachercoverspartofanimagewithasheetofpaper.Thediagramshowsseverallightraysthathavebeengivenoffbyaflashlight.Baseduponthelightraysyoucansee,drawwhereyouthinktheflashlightislocated.Thefollowingdiagramshowswhatyouseewhenyourteachercoverspartofanimagewithasheetofpaper.Thediagramshowsseverallightraysthathavebeengivenoffbyaflashlight.Baseduponthelightraysyoucansee,drawwhereyouthinktheflashlightislocated.
�67
Conclusion
1. ExplainwhyyoucanseeyourreflecConinamirrorbutnotinasheetofpaper.
�68
Lesson7.5–ScaBeringandReflecAng-Part2
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillexplainwhatyouhavelearnedaboutscaLeringandreflecCon.ThenapplywhatyouhavelearnedbyexplainingsomethingthatyouseealltheCmebutmightnotstoptothinkabout.
ProcedureThefollowingtwopicturesshowacaronadryroadandawetroad.
Conclusion
1. WhatdetermineswhetheranobjectwillscaLerlightorreflectlight?
2. Whyisitpossibletoseeyourselfinanobjectthatreflectslight,butnotinonethatscaLerslight?
�69
3. Using what you know about scattering and reflection, explain with words and/or drawings why it is possible to see an image of the car on the wet road but not on the dry road.
�70
Reading7.6–PolishingObjects
Ge`ngReadyLookatthisphotograph.ItisaphotoofsomethingmagnifiedmanyCmes.Whensomethingismagnified,itappearsmuchlargerthanyoureyeseesitbyjustlookingatit.PeoplesomeCmesrefertousingyoureyeswithnomagnifyingglassormicroscopeas“seeingwiththenakedeye.”Beforeyoureadthehints,takeaguess:Whatdoyouthinkthisphotois?
Herearefourhints:1. Youcankeepclothesinsomethingmadeofit.2.Youmaybesicngonitrightnow.2. Baseballplayersuseit.3. Itgrowsoutdoors.
Didyoufigureoutthatthisisapictureofwood?WhenwoodismagnifiedmanyCmes,itlookslikeCnytubes.SomeCmesthesurfaceofwoodiscoatedsothatitlooksshiny.Abaseballbatmighthaveashinysurface.Maybeyouhaveatableathomeorinschoolwithasurfacethatshines,butyoucannotseeyourreflecConinwoodaswellasyoucaninamirror.WhydoesyourreflecConinamirrorlookdifferentfromyourreflecConinwood?
WhyCanISeeMyReflecAoninSomeObjectsbutNotinOthers?Inclass,youdidaninvesCgaConusingalightsensortotracklightfromaflashlight.Youcomparedwhatthelightdidasitbouncedoffamirrorandoffasheetofpaper.Whenlightreachesasurface,itcanbereflectedoritcanbescaLered.YoulearnedthataTerthelightbouncedoffofamirror,allofthelightwentinaboutthesamedirecCon.ATerthelightbouncedoffofasheetofpaper,itwentinmanydirecCons.ReflecConiswhathappenswhenlightbouncesoffofasurfacethatisverysmooth.Amirrorhasaverysmoothsurface.Lookatthefollowingtwomodels.Theyshowtwodifferentwaysthatlightinteractswithasurface.
�71
ThemodelonthetopshowslightreflecCngoffofasmoothsurface,likeamirror.SeehowallofthearrowspointinaboutthesamedirecCon?Now,lookatthemodelontheboLom.ThearrowsinthismodelpointinmanydirecCons.Thisiswhathappenswhenlightbouncesoffofpaper.Paperseemssmooth,butifyoumagnifythesurface,likethephotoofwoodatthebeginningofthisreading,youcanseethatthesurfaceisbumpy.LightbouncingoffofabumpysurfaceisscaLered.ScaLeringiswhatoccurswhenlightbouncesoffofsurfacesthatarenotsmooth.ManyobjectsthatscaLerlightfeelsmoothwhenyoutouchthem.Asheetofpaperandawoodenbaseballbatfeelsmooth.However,ifyoucouldlookatthemwithapowerfulmicroscope,youwouldseethattheirsurfacesarebumpy.IfyoucouldtakeanobjectthatscaLerslight,likeapieceofwood,andsmoothoutallthebumpsandridges,thentheobjectwouldreflectmorelightandscaLerlesslight.Theprocessofsmoothingthemicroscopicbumpsandridgesonasurfaceiscalledpolishing.HowDoesaMirrorReallyWork?Inclass,yousawamodellikethisone.Yourteachercoveredthetopofitandaskedyoutoguesswhatwasunderneaththepaper.YoumayhavebeensurprisedtoseeaflashlightpoinCngdownwardinsteadofaflashlightpoinCngupward.InthisacCvity,youlearnedhowyoucanseeanimageofsomethinginamirror.Allofthelightraysarereflectedfromamirrorsotheybouncebacktoyoureyes,andtheylookliketheyarecomingfromanobjectontheothersideofthemirror.Ifthesurfaceofthemirrorisscratched,itwillscaLermoreofthelightthathitsit.Ifthemirroristooscratchedoruneven,somuchlightwillbescaLeredthatyoucannolongerseeaclearimageinthemirror.UsingMirrorstoSeetheStarsAstronomersareonetypeofscienCstswhousemirrors.Astronomersusetelescopestoproduceimagesofstarsandplanetsthatareveryfaraway.Telescopesusespeciallycurvedmirrorstoreflectlightfromstarstowardasensor.Thesensorusesthislighttoproduceapictureofthestars.Manyobjectsintheskydonotappearverybrightbecausetheyaresofaraway.ThismeansthatveryliLleofthelightthatcomesfromthemactuallyreachesEarth.Inordertogetthebestpictures,astronomersmustuseabigmirrorthatreflectsalotoflight,soithelpstoseeevenveryfaintobjects.Asmoothmirrorproducesaclearimagebecauseitreflectsalmostallthelighttothesensor,scaLeringveryliLle.PolishingaGiantTelescopeTheHaletelescopeattheMountPalomarObservatoryinCaliforniawasthelargesttelescopeintheworldformorethan50years.ThemainmirrorintheHaletelescopeis200inchesacross.Anaverage12-year-oldislessthan60inchestall.Themirrorisaboutasbigasthreeadultsstandingontopofeachother.Themirrorisverysmooth.IfyoucouldmagnifyitsothatitwasaswideastheAtlanCcOcean,thebiggestbumpyoucouldseeonitssurfacewouldbesmallerthan5cenCmetershigh.Itisverydifficulttomakeamirrorsosmooth.Ittookabout11yearsforpeopletopolishthismirrorbyhand.
�72
OtherThingsPeoplePolishtoReflectMoreLightPolishedmirrorsareimportanttoastronomers.Youprobablyusepolishedmirrors,too.Peoplepolishotherobjects—likerocks—tomakethemlookmoreshinyandpreLy,asyoucanseeinthesephotos.Adevicecalledarocktumblerwasusedtopolishtherocksinthephotographs.Arocktumblerhasasmallbarrelfilledwithrocks,water,andcoarsesand.Thebarrelrotatesslowlysothatthecoarsesandrubsoverthesurfaceofthebumpyrocks.Coarsesandsmoothesthelargebumpsontherocks.Thosearethebumpsthatyoudonotneedamicroscopetosee.Inthephoto,itiseasytoseethebumpsonthestonesontheleT.ATerawhile,thecoarsesandisreplacedwithfinersand.Sandthathasafinegraincansmoothoutsmallerbumpsthatyoucannotseeorfeel.ATerenoughCmeinarocktumbler,rocksandmineralsappearmuchshinierthantheywereatfirst.Why?Thepolishedrocksaresmoother,sotheyreflectmuchmoreofthelightthathitsthem.WhatMakesWoodLookShiny?Woodispolishedinadifferentway.Topolishwood,thesurfaceiscoveredwithaclearsubstance,likewax.ThewaxfillsalltheCnyholesinthewood.ATertheholesarefilled,thewoodhasasmoothsurfacethatreflectslightmuchbeLer.Thefollowingpicturesshowthedifferencebetweenawoodfloorwithwaxandonewithoutwax.WhyDoPeoplePolishThings?Peoplepolishsurfacesfordifferentreasons.Theypolishwood,rocks,andmineralsbecausetheylikethewaythefinishedobjectslookandfeel.Materialslikegoldanddiamondsarenotveryshinybeforetheyarepolished.Thediamondandgoldjewelrypeoplewearhasbeenpolished.Inscience,polishingisanimportantpartofmakinginstrumentsliketelescopesworkproperly.Instrumentslikethesecanhelppeoplelearnmoreabouttheuniverseinwhichtheylive.
1. Topolishleathershoes,peopleuseshoepolish.Whatdoesthistellyouaboutthesurfaceofleather?
2. MostobjectsthatcanbepolishedsCllscaLersomelight;noobjectcanhavepurereflecConwithoutanyscaLering.Why?
�73
Reading7.7–MoonPhases
Ge`ngReadyCanyouimaginetravelinginaspacecraTandthensteppingoutontothesurfaceofthemoon?OnJuly21,1969,theAmericanastronautNeilArmstrongbecamethefirstpersontowalkonthemoon.Asheputhisfootdown,Armstrongdeclared,“Thatisonesmallstepforman,onegiantleapformankind.”ArmstrongisoneofthefewpeoplewhohavebeenluckyenoughtoseehowEarthlooksfromthemoon.MostpeopleonlyseehowthemoonlooksfromEarth.Inthisreading,youwilllearnhowpeopleseethemoonfromEarth.Youwillalsolearnwhythemoon’sappearancechangeseveryday.Tounderstandthis,youneedtolearnwhytherearedaysandnightsonEarth.WhatMakesDayandNightHappen?Everydayyoucanseethesunasitseemstorisefromtheeasternhorizon,moveacrossthesky,andsetinthewest.WhatpeoplesomeCmesdonotunderstandisthatthesunisnotreallymovingatall.ItonlyseemstomovebecausetheEarthspinsaround,carryingpeopleinandoutofviewofthesun.Youseethesunduringthedaybecauseyouareonthepartoftheearthfacingthesun.Youdonotseeitatnightbecausetheearthhasspunsothatyouareonthesideturnedawayfromthesun.Imaginethatyouaresicngonachairthatcanspin,andafriendisstandingbesideyouholdingacandle.Asyouspinslowlyinthechair,youfirstseethecandleoutofthecornerofoneeye,movingfromthesideunClitisrightinfrontofyou.ThenitseemstomovetotheothersideunClitdisappearsbecauseitisbehindyou.Ifyoudidnotknowyouwerespinning,youmightthinkthatthecandlewasmovingaroundyouinacircle.Thesamethinghappenswiththeearthandthesun.Insteadofthechair,theearthistheobjectthatisspinning.PeopleareseatedonthesurfaceoftheearthasitpointstheminthedirecConofthesunandthenawayfromit.Thissamethinghappenseverysingleday.YouexperiencesunriseandsunsetbecauseEarthspinsonitsaxis.Soactuallythetermssunriseandsunsetaremisleading,sincethesundoesnotactuallymovearoundEarth;itjustappearstodoso.Earth’saxisisanimaginarylinethatrunsfromtheNorthPoletotheSouthPoleandthroughthemiddleoftheearth.Earthcompletesafullturnarounditsaxisonceeveryday.Thatmeansittakes24hoursforEarthtodoacompleteturn.Earth’sspinningisthereasonwhypeopleexperiencedayandnight.OnehalfofEarthfacesthesunandislitup,soitisdayCmethere.AtthesameCme,theotherhalfofEarthfacesawayfromthesun.Thesun’sraysareblocked,soitisdark(ornighcme)onthatsideoftheearth.AsEarthspinsonitsaxis,differentpartsturntofacethesunortofaceawayfromit.ThisiswhatcausespeopleonEarthtoexperiencedayandnight.
�74
RoundandRoundTheyGo
AtthesameCmethatEarthspinsonitsaxis,italsomovesaroundthesunonapathcalledanorbit.Earth’sorbitaroundthesuntakesabout365days(oneyear)tocomplete.AtthesameCmethatEarthrevolvesaroundthesun,themoonisalsoorbiCngaroundEarth.AfullorbitofthemoonaroundEarthtakesabout28days(onemonth)tocomplete.TheseprocessesexplainwhypeopleonEarthexperiencedaysandnights,andthemoonlooksdifferentatdifferentCmesofeachmonth.Allofthesearerelatedinsomewaytolight.Thisreadingwillfocusonhowpeopleseethemoonandwhythemoon’sshapechangeseveryday.HowDoPeopleSeetheMoon?Foryoutoseeanobject,iteitherneedstobealightsourceoritneedstobelitbyalightsource.Thesunisalightsource,whichiswhyyoucanseeit.Themoon,ontheotherhand,isnotalightsource.Yet,youcansCllseeit.Theonlythingthatcouldbehappeningisthatthemoonisbeinglitbysomeotherlightsource.CanyoutellfromthemodelwhatislighCngthemoonsothatyoucanseeit?Thelightsourcethatshinesonthemoonisthesun.Halfofthemoonisalwayslitbythesun,justlikehalfoftheearthisalwayslitbythesun.Youcanneverseethedarksideofthemoon,becausenolightreachesit.Ifnolightreachesit,nolightcanbescaLeredfromittoyoureyes.ThinkaboutthefourcondiConsneededforyoutoseeanobject.HowarethesecondiConsmetinthecaseofseeingthemoonfromEarth?Lookatthediagramtohelpyouexplain.
Foryoutoseethesideofthemoonthatislitbythesun,someofthesun’slightthatisscaLeredbythemoonneedstoreachyoureyeshereonEarth.MoonriseandMoonsetWhenyouarestandingonEarth,themoonappearstomoveacrossthenightskyjustasthesunappearstomoveduringtheday.Infact,Earthspinningarounditsaxiscausesthemoontoriseintheeastandsetinthewest,justlikethesun.ManyCmes,themoonrisesduringthedayinsteadofduringthenight.Ifwelookcloselywecanseeit,butweusuallydonotnoCceit.Why?
�75
WhatMakesaFullMoonoraHalfMoon?Dependingonwhenyoulookatthemoon,youmightseeafullmoon,ahalfmoon,aCnysliverofamoon,ornomoonatall.Infact,themoonisalwaysthere,andhalfofitisalwayslitbythesun.WhetheryouseeitornotandwhatshapeyouseedependsontheposiConofthemooninrelaContothesunandEarth.FromEarth,youcanonlyseethepartofthemoonthatisfacingEarth.Thisisnotnecessarilythepartofthemoonlitbythesun.Thisiswhy,mostoftheCme,wedonotseeafully-illuminatedcircle,butonlypartofit.Thechangingshapethatyouseeiscalledaphaseofthemoon.ThephaseisthepartofthemoonthatisbothlitbythesunandseenfromEarth.ThephasesofthemoonchangeinacyclestarCngwiththenewmoon(alsocalledthedarkmoon).Becauseittakes28daysforthemoontogoaroundEarth,thechangingshapethatyouseerepeatsevery28days.Lookatthemodeltoseethecycleofphasesandthenamesofeachphase.Waningmeansshrinking,waxingmeansgrowing,andgibbousmeansswollen.YoumaychoosetosearchontheInternetforvideoillustraCngandexplainingthemoon’sphases.TobeLerunderstandhowyouseephasesofthemoon,itmighthelptolookattwophasesmoreclosely.NewMoon(orDarkMoon)AnewmoonexistswhenthemoonisbetweenthesunandEarth.Atthatpoint,thelitsideofthemoonisfacingdirectlyawayfromEarth,soyoucannotseeit.ThesideofthemoonfacingEarthisnotlit,soitisdark.Whenyoulookinthenightsky,youmaythinkthatthereisnomoonatall.ThesunisreflecCngoffofthesurfaceofthemoon,butifyoudrewthearrowsinthepreviousdiagram,youwouldseethatnoneofthelightisreachingtheeyesofpeopleonEarth.FullMoonAfullmoonexistswhenEarthisbetweenthesunandthemoon.ItisimportantforyoutonoCcethelinesoftheorbitsforthistomakesense.RememberthatthemoonisorbiCngEarth;itisnotorbiCngthesun.WhenthelitsideofthemoonisfacingEarth,youseeabigcircleofmoonthatiscalledafullmoon.Thedarksideofthemoon(thesidethatisnotilluminatedbythesun)isfacingawayfromEarth.Becausethecycleofthemoon’sphasesrepeatsevery
�76
28days,itispossibletousethepreviousmodelstopredictthemoon’sphaseonanygivendate.IfyouhaveaccesstotheInternet,youcanlookupcalendarsofphasesofthemoon.Drawamodelexplainingwhythemoonwilllookthewayitwillonyournextbirthday.Ifyouarenotsure,takealookatthemodelsontheotherpagesinthisreading.Insteadofusingthecomputer,youcouldalsochooseoneofthemoon’sotherphases(notafullornewmoon)anddrawamodeltoexplainwhyitwouldlookthatwayonEarth.
�77
�78
Lesson8–TransmissionofLightLesson8.1–Whydoesthemoonchange?
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillinvesCgatewhatcausesthephasesofthemoon.
ProcedurePart1
Pretendthataping-pongballisthemoon.Theskewerthroughtheballletsyouholditmoreeasily,butitdoesnotrepresentanything.SincetheposiConofthesunbarelychangesasthemoonrevolvesaroundEarth,itisimportantthatyoukeepthewhitehalfoftheping-pongball(thesideofthemoon)facingthesunduringthisacCvity.HoldtheendoftheskewerwiththeballturnedsothatthewhitehalfistoyourleTandtheblackhalfistoyourright.Yourarmshouldbestraightoutinfrontofyou.ImaginethatthesunisonyourleTthroughoutthisacCvity.Nowlookattheball(themoon)anddrawwhatyousee.
Nowmoveyourarm,sClloutstretched,45°totheleT,withouttwisCngtheskewer,sothatthewhitehalfoftheballsCllpointsinthesamedirecConasbefore—totheleT.Whilethemoonhasmoved45°totheleT,neithertheearth(you)northesunhave;thesunissClltotheleT.ThatiswhythewhitesideofthemoonsCllhastofaceleT,eventhoughthemoonhasmoved.Onceagain,lookattheball(themoon)anddrawwhatyousee.
Moveyourarm45°farther,sothatthemoonisallthewaytoyourleT.ThewhitesideshouldsCllbefacingleT,awayfromyou.Drawwhatyousee.
PutyourarminthesameposiConyoustartedin—straightoutinfrontofyou.Now,moveit45°
�79
PutyourarminthesameposiConyoustartedin—straightoutinfrontofyou.Now,moveit45°totheright,keepingthewhitesidefacingtheleT,towardthesun.Drawwhatyousee.
Nowmoveyourarm45°totherightagain.Yourarmshouldbeouttoyourrightside.Thewhitesideoftheball—thelitsideofthemoon—shouldsCllbefacingthesun.Drawwhatyousee.
LookatReading6.4.Usethediagramtocompareyourdrawingsoftheballtothephasesofthemoon.Addthepropernamestothephasesofthemoonrepresentedinyourdrawings.
Part2ThreestudentswillparCcipateinthenextpartoftheacCvity.Onewillsitonaswivelchair.ThispersonwillbeEarth,andEarthshouldrevolveslowlytosimulateEarthspinningonitsaxis.Anotherpersonwillstandtotheside,poinCngalitflashlightatEarth.Thatpersonwillrepresentthesun.Theteacherwilldarkentheroom.WhyistheflashlightapoorsimulaConofthesun?
WhichsideofEarthisindayCmeandwhichsideisinnighcmeduringthisacCvity?
Whatcausesittobedarkduringthenighteventhoughthesunisalwaysshining?
Athirdpersonwillrepresentthemoon.ThispersonwillrevolveslowlyaroundEarth.Thisvolunteershouldwalkveryslowly—muchslowerthanEarthspins.HowmanyrevoluConsonitsaxisdoesEarthcompleteintheCmeittakesthemoontogooncearoundEarth?
�80
IsthemoonmoreoTeninthenightsky(onthenightsideofEarth)orinthedaysky(onthedaysideofEarth)?Whydowealwaysthinkofthemoonasbeingintheskyduringthenightandnotduringtheday?
Atagivenmoment,whereonEarthcanyouseethesunrising?
Conclusion
1. InthefirstpartofthisacCvity,halfofthemoonwasblackbecauseitwaspaintedblack.Inreality,whyishalfofthemoonalwaysblack?
2. Whydoesthemoonappeartohavedifferentshapesduringdifferentpartsofthemonth?
�81
�82
Lesson8.2–EvaluaAngtheLightModel
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillevaluateourcurrentmodeloflighttoseeifithelpsusexplainwhywecanseethroughsomeobjectsbutnotothers.
Procedure-Part1Inthefollowingspace,drawthelightmodeltoexplainwhyyoucannotseeanobjectwhenthereisacardboarddividerbetweenyoureyeandtheobject.
PredicAon:
1. Accordingtothelightmodel,whathappenstolightwhenitreachesanobject?
2. Inthatcase,whatdoesthelightmodelpredictyouwillseeifyoureplacethecard-boarddividerinthelightboxwithaclearplasCcdivider?
�83
Procedure-Part2Putthecardboarddividerinthelightbox.Lookattheobjectinthebox.Talkwithyourgroupaboutwhatthelightisdoingsothatyoucanorcannotseetheobject.NowreplacethecardboarddividerwithaclearplasCcdivider.Lookattheobjectagain.Talkwithyourgroupaboutwhatthelightisdoingsothatyoucanorcannotseetheobject.Whydoestheconsensusmodelnothelpyouexplainhowyouwereabletoseetheobjectthroughthetransparency?
ThelightmodelneedstoberevisedtoexplainthatyoucanseeanobjectinthelightboxthroughaclearplasCcdivider.
Drawthelightmodelsothatitexplainsthefollowing:Howcanyouseeanobjectontheoppositesideofacleardivider?Whyisitpossibletoseethecleardivideritself?
Howdoesyourdrawingshowthatitispossibletoseetheobjectthroughthedivider?
Howdoesyourdrawingshowthatitispossibletoseethedivideritself?
�84
Lesson8.3–MeasuringLightTransmission
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillcompareournaked-eyeobservaConsoftransmissionwithmeasurementstakenbyinstruments.
PredicAon:
ProcedureUsethefollowingtabletoordertheobjectsyouhavecollectedaccordingtohowmuchlighttheytransmit.Theobjectthattransmitsthemostlightshouldbea“1”.Theobjectwiththelowesttransmissionshouldbea“5”.UsealightsensortomeasuretheamountoflighttransmiLedthrougheachobject.Recordthedatainthedatatable.Ranktheobjectsbasedonthelightsensordata.
Data
Object Prediction (1-6)
Light measurement Transmission Rank (1-6)
No object between the light source and the sensor.
�85
Conclusion
1. Lookatthelistsanothergroupmadefortheobjectsyoucollected.WhichlistmatchesbeLer?TheonemadebyesCmaCngtheamountoftransmiLedlightwithyoureyes,ortheonemadebymeasuringlightusingthelightsensors?
2. WhataresomereasonswhymeasurementdeviceswereusefulinthisinvesCgaCon?
�86
Lesson8.4–RevisingtheLightModel
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillusethelightmodeltopredictwhyitispossibletoseethroughsomeobjectsbutnotthroughothers.
ProcedureThefollowingdiagramshowslightleavingasourceandhicngapieceofglass.Drawwhatyouthinkwillhappentothelightraysastheyhittheglass.(Hint:Canyouseethroughglass?CanyouseeareflecConofyourselfinglass?)
Thefollowingdiagramshowslightleavingasourceandhicngapieceofunpolishedwood.Drawwhatyouthinkwillhappentothelightraysastheyhitthewood.(Hints:Canyouseethroughwood?CanyouseeyourreflecCononawoodsurface?)
�87
Conclusion
1. InLesson6,youlookedataphotoofpapertakenwithamicroscope.Yousawthatpaperismadeoffibers,andyoulearnedthatlightscaLersoffthesurfaceofpaper.Imaginethatapersonislookingthroughasheetofpaper,asshowninthethefollowingincompletemodel.Imaginethatthepersoncanbarelyseethelightsourcethroughthepaper.Completethemodelbydrawingarrowstoshowthis.
�88
Lesson8.5–TransmissionofLight
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillexaminemoreexamplesoftransmissionandreflecConoflight.WhenweinvesCgate,think,talk,andwriteaboutscience,weunderstanditbeLer.Lightfromaflashlightisshownhicngtwodifferentobjectsbelow.1. Completeeachdiagram,sothatitshowshowmuchlightyouthinkeachobjectwilltransmit.2. MakesuretoshowwhetherlightthatbouncesofftheobjectwillbescaLeredorreflected.
ReflecAveSunglassesSomesunglasseshaveareflecCvecoaCng.ThecoaCngmakesthemlooklikeamirror,butitsCllallowsthepersontosee.
RicePaperRicepaperisusedinplaceslikeJapantomakedoorsthatletlightthrough.Thepictureshowsadoormadewithricepaper.
Conclusion
1. ATerEvacleanedtheslidingglassdooratherhouse,herfriendcameoverandwalkedrightintoit.Whyisiteasiertoseetheglasswhenitisdirtythanwhenitisclean?
�89
�90
Reading8.6–UsinglightinopAcalfibers
Ge`ngReadyHaveyoueverseenalamplikethisone?ThelamphashundredsofthinplasCcfiberscomingoutofit.TheendsofthefibersglowwithaCnylight.TheseCnystrandsarecalledopCcalfibers.OpCcalfibersareusedtomakefunlamps,buttheyarealsousedinotherwaystomakeyourlifeeasier.EveryCmeyougoontheInternet,yousendandreceiveinformaConusingopCcalfibers.OpCcalfibersalsomakeitpossibleforatelevisiontogethundredsofchannels.Inthisreading,youwilllearnaboutopCcalfibersandhowtheywork.TheyareoneofthewaysthatscienCstscreatenewthings,becausetheyunderstandlight.
HowDoOpAcalFibersWork?LookaroundyourhouseforapieceofclearplasCc.YoumightfindaCDcase,asodapopboLle,orplasCcwrapfromthekitchen.NoCcethatyoucanseethroughtheclearplasCc.ExplainhowitispossibletoseesomethingontheothersideoftheplasCc,eventhoughtheplasCcisblockingthepathbetweentheobjectandyoureye.
LookcarefullyattheplasCcsurface.ExplainhowitispossibleforittotransmitlightandforyoutoalsoseeyourreflecCon.
WhatDoesPlasAcHavetoDowithOpAcalFibers?OpCcalfibersworkbecauselightisreflectedandtransmiLedbymaterialsinthefiber.MostopCcalfibersaremadeofglasssurroundedbyothermaterials.Lighttravelsintothecorebecauseclearglasstransmitslighteasily.WhatmakesopCcalfibersspecialiswhathappenswhenthetransmiLedlighthitsthesideoftheclearglasscore—itisreflectedlikeitwouldfromamirror.Becausethelightisreflected,itcanfollowalongthefiber,evenwhenthefiberisbent.ThisiswhyopCcalfibersaresomeCmescalled“lightpipes.”PeoplecandirectlightdownanopCcalfibermuchliketheycandirectwaterthroughawaterpipe.NotethepictureofabeelookingintoathickpieceofopCcalfiber.WhileitlookslikethereisanotherbeecomingoutoftheopCcalfiber,youarereallyjustseeinglightthathasbeenscaLeredfromthebee,transmiLed,anddirectedalongthebentfiber.HowDoesOurLightModelApplytoWhatHappensinOpAcalFibers?Inclass,youcreatedaconsensusmodeltodescribehowlighthelpsyousee.Inthismodel,youdrewlightasstraightlinesthatgooutinalldirecConsfromalightsource.Iflightbouncesoffanobject,itchangesdirecConsandthentravelsinastraightlineagain.Youdrewlightasstraightlinesbecausewhenlighttravelsthroughtheair,itmovesinastraightline.LightalsomovesinastraightlineinanopCcalfiber.Lightdoesnotbend;itjustseemstobendasitchangesdirecConwhenitisreflectedatthesides.Ifyoushineaflashlightintheair,thelightwillfollowastraightpathunClithitsanobject.IfyoushineaflashlightintooneendofanopCcalfiber,thelightwillfollowthepathofthecableandcome
�91
outtheotherend.Gobackandlookatthepictureofthelampatthebeginningofthisreading.Theendsofthefibersarebright,becauselightfromthelamphasfollowedthefibersandisleavingthemattheotherend.
HowAreOpAcalFibersUseful?Youmayalreadyknowthatcomputerscommunicatewitheachotherusingelectricalwires.ComputerscanalsocommunicatebyshininglightdownopCcalfibers.Whywouldpeopleprefertosendsignalsdownafiberusinglightinsteadofdownawireusingelectricity?OnereasonisthatopCcalfiberscanbemuchthinnerthanelectricalwires.Boththewirebundleandasinglefibercandothesamejob.Asinglefibercandotheworkofmanyelectricalwires.HaveyouevertriedtoloadawebpageandhadtowaitalongCme?Thishappensbecausemanycomputersaretryingtosendsignalsdownthesamewires.Tryingtosendmanysignalsdownthesamewireisliketryingtodrivealotofcarsonthesameroad.Iftherearetoomanycarsontheroad,therewillbeatrafficjam.BecauseopCcalfibersaresmallerbutcancarrymoresignalsatonce,theycanhelptopreventtrafficjamsthathappenontheInternet.ThisiswhysomepeoplecalltheInternettheinformaConsuperhighway.NewwaysofcommunicaCngareeverywhere.Televisionhaschangedalotsinceyourparentsorgrandparentswereyoung.Askaparent,grandparent,oranotherolderpersonthefollowingquesConsabouttelevision:
• HowmanychannelscouldtheygetonTVwhentheywereyourage?
• HowdidtheTVrecepConcomparetotoday?
WhydoyouthinkthesituaContodayisdifferentthanwhattheydescribed?Describewhatyoulearned.
UsingOpAcalFibers:SurgeryWhendoctorsdosurgery,theymustbeabletoseeinsideapaCent’sbody.Usually,theyhavetocutintoskin.ByusingopCcalfibers,doctorscanmakeveryCnycutsandleavescarsthatarealmostinvisible.ATermakingaCnycut,doctorsinsertasmallopCcalfiber.TheycanlightuptheinsideofthepaCent’sbodybysendinglightthroughthefiber.Whenthelighthitssomethinginsidethebody,itbouncesoffandentersasecondopCcalfiber.Thesecondcablecarriesthelighttoacamera.Thecameraproducesapicturethatthedoctorcanseeonatelevisionscreen.OpCcalfibershavemadesurgerymuchsaferforpaCents.UsingOpAcalFibers:LighAngHaveyoueverbeeninaroomwithnowindows?Manypeoplewhoworkinofficebuildingsdothiseveryday.SomescienCstsareworkingwithopCcalfiberstochangethat.BypucngoneendofanopCcalfiberoutside,itispossibletosendsunlighttoaroomthathasnowindows.OpCcalfibersmaysomedayprovidesunlightforpeoplewithnowindows,eveniftheyareunderground.OpCcalfiberscanprovidepeoplewithnaturalsunlightforfree,butwhataresomedisadvantagestousingopCcalfiberstolightaroomwithsunlight?
�92
WhyAreOpAcalFibersImportant?OpCcalfibersallowpeopletouselightforalotofnewpurposes.Peoplecansendsignalsbetweencomputers,andtheycandomuchsafersurgeries.Tosendlightdownacable,opCcalfibersrelyonreflecCngandtransmicnglight.Thesearetwodifferentwaysthatlightcaninteractwithobjectsandmaterials.Inthenextlesson,youwilllearnaboutathirdwaythatlightcaninteractwithobjectsandmaterials,andyouwillbegintoimaginenewpossibiliCesforthefuture.
�93
�94
Lesson9–AbsorpAonofLightLesson9.1–Lightmakesthingshappen
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillinvesCgateanotherwaylightcaninteractwithobjects.Lightcanalsobeabsorbed.
ProcedureYourteacherwillshowyouaradiometer,whichspinswhenlightshinesonit.
Inthefollowingtable,listotherobjectsyouhaveseenthatwhenlighthitsthem,somethinghappens.Describewhathappenswhenlightisshinedoneachobject.
Data
Conclusion
1. Theobjectsonyourlistallabsorblightandthensomethinghappens.WhichobjectsonyourlistalsoscaLer,reflect,ortransmitlight?
Object What happens when light shines on the object? v
�95
�96
Lesson9.2–InvesAgaAngheaAngbylight
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillinvesCgatehowlightinteractswithwater.ATercollecCngdata,wewillreviseourmodelsoitcanexplainwhysunlightfeelswarm.
ProcedureAbrightlightwillbeshinedontwobeakersofwater.Onebeakercontainsclearwater,andtheothercontainswatercoloredwithfoodcoloring.Predictwhichbeakerofwaterwillgetwarmer:thecoloredwaterortheclearwater.Explainwhyyouthinkso.
AlightsensorandathermometerwillbeusedtotakeseveralmeasurementsduringthisinvesCgaCon:
amountofreflectedlightamountoftransmiLedlightstarCngwatertemperatureendingwatertemperature
Createadatatabletorecordthemeasurementsfortheclearwaterandthecoloredwater.
Data
Conclusion
1. Howdoestheamountoflightreachingthecoloredwatercomparewiththeamountreachingtheclearwater?Howdoyouknowthis?
Variable Clear Water Dark Water
�97
2.Thefollowingwillhelpyouuseyourdatatounderstandwhyonebeakerofwatergotwarmerthantheother.3.AddtheamountofreflectedlighttotheamountoftransmiLedlightfortheclearwater.
4.AddtheamountofreflectedlighttotheamountoftransmiLedlightforthecoloredwater.
5.Howisthetotalamountoflightthatyoumeasured(lightthatwasreflectedandtransmiLed)relatedtotheamountofheaCng?
6.Whatdoyouthinkhappenedtothelightthatcausedthewatertoheatup?Ifithelpsyou,draw(construct)twomodelsofwhathappenstothelightinthecaseofcoloredwaterandclearwater.
Light Reflected
Light Transmitted
Total Light Measured
Light Reflected
Light Transmitted
Total Light Measured
�98
Reading9.3–SolarPowerPlants
Ge`ngReadyInclass,youareinvesCgaCnghowlightcanbeusedtoheatwater.Whataresomereasonspeoplewouldwanthotwaterorsteam?
Didyouknowthatsteamcanalsobeusedtogenerateelectricity?Inthisreading,youwilllearnmoreabouthowlightmakesthingshappen.Forexample,lightcanbeusedtogeneratesteam,whichcangenerateelectricity.UsingSteamtoDoThingsAlmostalloftheelectricitythatpeopleusetolightlamps,tokeepfoodcoldinrefrigerators,ortowatchtelevisionisgeneratedbyamachinecalledasteamturbine.Youdonothaveasteamturbineinyourhome.Somewhere,atsomepowerplant,asteamturbinegenerateselectricityandsendsitthroughwires.Asteamturbineisamachinewithgiantfanbladesinside.Whenthefanbladesturn,themachineusestheturningmoContogenerateelectricity.Thetrickistofigureoutawaytomakethefanbladesturn.Youcanthinkofthebladesinsideasteamturbinelikeagiantpinwheel.Whenyoublowonapinwheel,theairyoubreatheouthitsthebladesofthepinwheelandmovethem.Now,imaginethatyoucouldholdthepinwheelaboveapotofboilingwater.Thesteamwouldalsomakethepinwheelturn,justlikewithyoublowingonit.Makingapinwheelturnbyholdingitaboveboilingwateristhesameideaasusingsteamtoturnthefanbladesinsideasteamturbine.Longago,someoneneededtofigureouthowtoheatwaterenoughsothatitturnstosteam.Thenthesteamcouldoperatetheturbineandgenerateelectricityforpeople’shomes.MostoftheelectricitygeneratedintheUnitedStatesisproducedbycoalpowerplants,whichburncoaltoheatwaterunClitbecomessteam.SolarPowerInclass,youareinvesCgaCnghowlightfromalightbulbcanbeusedtoheatwaterinabeaker.Somepowerplants,calledsolarpowertowers,uselightfromthesuntoheatwaterunClitbecomessteam.Asolarpowertowerusesthousandsofmirrorstoreflectlightfromthesuntoatowerthatholdswater.Lookatthephototoseehowthislooks.Whenlightreflectedbythemirrorshitsthetower,thewaterinsideisheated.Ifthewaterisheatedenough,itbecomessteam.Thesteamistransportedthroughpipestoasteamturbine,whichproduceselectricity.Onedrawbackofasolarpowertoweristhatitcanonlyheatwaterduringtheday.Oncethesteamcoolsdownandbecomeswateragain,itcannotturnthesteamturbines.PeoplesCllneedelectricityatnightorwhenthesunisblockedbyclouds.ToproduceelectricityattheseCmes,somesolarpowertowersheatadifferentliquidinsteadofheaCngwater.Oncethefluidisheated,itcanbetransportedthroughpipestocomeincontactwithacontainerofwater.There,itheatsthewatertomakesteam.IttakesthespecialfluidalongCmetocooldown,soitcanremainveryhotthroughout
�99
thenight.Becausethefluidstayshot,itcanheatwatertocreatesteamevenwhenthesunisnotshining.
SolarChimneysAnotherwaytouselightfromthesuntogenerateelectricitydoesnotinvolveheaCngwateratall.Inasolarchimney,lightfromthesunheatstheairunderneathalargeglassroof.Thehotairrisesandisforcedthroughagiantchimney.Astheheatedairrises,itturnsfanbladestogenerateelectricity.Thesuncanonlyheatairduringtheday,sosolarchimneyshavepipesfilledwithliquidthatremainshotatnight.Thatmeansthesolarchimneyworksevenwhenthesunisnotshining.Lightfromthesuncanheatanobjectwhenithitsit.Thisiswhyyourskinfeelswarminthesunlight.IntheinvesCgaConyouaredoinginclass,youwilldeterminehowlightheatsthingsandwhysomematerialsgethotfasterthanothers.Thelightyourteacherusestoheatbeakersofwateriscalledafloodlamp.NoCcethatafloodlamphassilversidesdesignedtoreflectlight.Inwhatwaydoesthefloodlampworktoheatwaterfasterthanaregularlightbulb?
YouhavelearnedthatlightcanbescaLered(orreflectediftheobjectissmooth)ortransmiLedwhenitreachesanobject.Inclass,youusedlighttoheattwobeakersofwater.IfallthelightthatreachedthebeakerswasscaLeredorreflected,howhotwouldthewaterbe?
HowhotwouldthewaterbeifallthelightreachingthetwobeakershadbeentransmiLed?
�100
Lesson9.4–KeepingTrackofLight
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillreviseourlightmodeltoaccountforallthreewaysthatlightcaninteractwithobjectsandmaterials.ObjectscanreflectorscaLer,transmit,andabsorblight.
ObservaAons
DuringthelastacCvity,youinvesCgatedwhathappenedasabeakerofclearwaterandabeakerofcoloredwaterwereheatedusinglightfromafloodlamp.Basedonwhatyousawinthatexperiment,answerthefollowingquesCons.1. WhichbeakertransmiLedmorelight?
2.Whichbeakerreflectedmorelight?
3.Whichbeakerabsorbedmorelight?
4.Whatevidenceshowedwhichbeakerabsorbedmorelight?
�101
Conclusion
1. Thesediagramsshowtwoincompletemodelsinwhichlightisleavingafloodlampandtravelingtowardabeakerofwater.CompletethefollowingmodelsbydrawingaddiConallightraysthatcanbeusedtoexplainyourobservaCons.Makesureofthefollowing:
•Yourmodelsshowthesameamountoflightreachingbothbeakers.•Onemodelshowsdifferentamountsoflightbeingreflected,transmiLed,andabsorbedthantheother.
�102
Lesson9.5–RevisiAngphenomenacausedbylight
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillexaminehowdevicesusereflecConorscaLering,transmission,andabsorpContomakethingshappen.
ProcedureLookattheobjectyourteachershowsyou.Doestheobjectreflect/scaLeralotoflight?Howdoyouknow?
Doestheobjecttransmitalotoflight?Howdoyouknow?
Doestheobjectabsorbalotoflight?Howdoyouknow?
Conclusion
1. InseveralacCviCesyousawthatlightwasscaLered,transmiLed,absorbed,orsomecombinaConofthese.IntheacCvitywiththeclearandcoloredwater,yousawthatthemorelightthatwasabsorbed,thelessthatwasscaLeredandtransmiLed.IsthisrelaConshiptruefortheobjectyourteacherjustshowedyou?MakeageneralruleaboutthewaytheamountsoflightreflectedorscaLered,transmiLed,andabsorbedbyanyobjectarerelatedtoeachother.
2. Ifyoudesignedadevicethatuseslighttomakesomethinghappen,likeheaCngsomething,makingsomethingmove,orgeneraCngelectricity,wouldyouwantmostofthelightthatreachesthedevicetobereflected,transmiLed,orabsorbed?Why?
�103
�104
Lesson9.6–AbsorpAonofLight
Whatwasthepointofthelastlesson?
ProcedureApplywhatwehavelearnedaboutlighttosituaConsthathappenoutsideofscienceclass.TwopotatoesareleTinthesunshineforanhour.Onepotatoiscoveredwithaluminumfoil.Theotherpotatohasnothingcoveringit.ATertheendofthehour,whichpotatowillbewarmer?Explain.Asolarcelluseslightfromthesuntorunelectronicdeviceslikecalculators.SolarcellshaveacoaCngthatreflectsasliLlelightaspossible.Whywouldthisbeimportant?Lightfromthesameflashlightisshinedonseveralobjects.AlightdetectormeasuresthelightaTerithitseachobject.Usethefollowingdatatodeterminewhichobjectabsorbedthemostlight.Whichobjectabsorbedthemostlight?Explain.
Conclusion
1. Whichobjectabsorbedthemostlight?Explain.
2. WhichobjecttransmiBedthemostlight?Explain.
Object Light Scattered Light Transmitted
T-Shirt 131 Lux 14 Lux
Cardboard 180 Lux 2 Lux
Ice Cube 450 Lux 100 Lux
Brick 157 Lux 0 Lux
�105
�106
Reading9.7–SolarEnergy
Ge`ngReadyHaveyouevergoneintoaroomwherethesunwasshiningbrightlythroughthewindows?Ifso,howdidthetemperatureinthisroomcomparetothetemperatureofotherrooms?Inclass,youlearnedthatlightcaninteractwithobjectsinthreeways.Lightcanbereflected(orscaLered),transmiLed,andabsorbed.Whenlighthitsanobject,one,ortwo,orallofthesecanhappenatthesameCme.Whenlightfromthesunreachesaclearwindow,someofthelightisreflectedoffofthesmoothglass.Someofthelightisabsorbedbytheglass,butmostofthelightistransmiLed.MostofthelightconCnuestotravelunClitreachesanobjectintheroom,likethefloor,walls,orfurniture.TheseobjectsthenscaLer,transmit,andabsorbthelightthatreachesthem.Thelightabsorbedbytheobjectscausesthemtoheatup.Theseheatedobjectscanthenheatotherstuffintheroom,suchastheair,theceiling,andevenyou.Today,youwillreadaboutmanywaysthatpeopleusesunlight,becausetheyunderstandthatlightcanmakethingshappen.HowDoPeopleUseReflecAon?Haveyoueverseenabuildingthatlooksasifitweremadeoutofmirrors?ThesebuildingsaremadeusingreflecCveglass.HowwouldreplacingclearwindowswithreflecCveglassaffectthetemperatureinsidethebuilding?Explainyourideas.
Inclass,yousawthatlightcancausemanytypesofchangesinobjectsbesidesheaCngthem.Lightmakesplantsgrow,radiometersspin,andlight-sensiCvepaperchangecolor.Youlearnedthatinorderforthesechangestooccur,lightreachingtheobjectmustbeabsorbed.Lightcarriesenergyasittravels,sowhenlightisabsorbedbyanobject,energyistransferredfromthelighttotheobjectthatithits.Itisthetransferofenergythatenablesobjectstoheatup,spin,grow,orchangecolor.Theenergycarriedbythelightfromthesuniscalledlightenergyorsolarenergy.Solarenergycanbeusedinmanyways.
SolarWaterHeatersSolarenergyiswidelyavailableinCaliforniabecauseitisverysunny.PeoplewholiveinCaliforniahavebeenusingsolarenergyfromthesunforalongCme.Somepeopleusesolarenergycarriedbylightfromthesuntoheattheirwater.SolarwaterheatersareoTenplacedonroofstoabsorbsunlightdirectly.PeopleinsouthernCaliforniahavebeenusingsolarwaterheatersforoverahundredyears.Byusingsolarenergy,peopledonotneedtopayforthegasorelectricitythatpowermostwaterheaters.Mostsolarwaterheatershavethreeparts:ahotwaterstoragetank,asolarcollectorthatabsorbslightfromthesun,andabackupgasorelectricheaterthatcanheatthewaterincaseofacloudyday.Lookatthepictureofthesolarwaterheater.ItisdesignedtoabsorbasmuchlightaspossibleandreflectasliLlelightaspossible.
�107
ThinkoftheacCvityyoudidinclasswhenyouusedalightbulbtoheatabeakerofclearwaterandabeakerofcoloredwater.UsewhatyoulearnedfromthatacCvitytohelpyouexplainwhyitisbestforsolarcollectorstobeblack.
Doyouthinkusingsolarwaterheaterswouldbeagoodideawhereyoulive?Why?
HowDoesSolarEnergyMakeElectronicsWork?HeaCngwaterisnottheonlywaytousesolarenergy.Haveyoueverseenasignthatlooksliketheoneinthephotograph?Togetpeople’saLenCon,lightsflashaboveandbelowthesign.Theselightsneedelectricitytooperate,buttheydonotneedtobepluggedin.Thedarkpanelontopofthesigniscalledasolarcell.Itissimilartothesolarcollectorsyoujustreadabout.Asolarcellproduceselectricitybyusinglightenergyfromthesun.Solarcellsareusefulforthingsthatneedelectricitybutarenotnearanelectricaloutlet.StateslikeNewMexicoandArizonausealotofsolarcellsbecausetheyhavealotofsunlight,andmanydesertareasarefarfromelectricity.Solarcellsarealsousefultomovethings.Forexample,scienCstscanbuildcarsthatneverneedgasoline.Thesecarshavesolarcells,sotheymoveusinglightenergyfromthesun.SolarPanelPowersCalculatorSomecalculatorsaredesignedtooperateusingasmallsolarcell.Likethesolarcollectorsonsolarwaterheaters,solarcellsaredesignedtoabsorbalotoflightandtoreflectveryliLle.Explainwhyagoodsolarcellabsorbsalotoflightandreflectsasmallamountoflight.Someminiaturecarscanrunusingsmallsolarcells,butthesolarcellsneededtorunarealcarmustbeverylarge.Usingwhatyouknowaboutsolarenergy,explainwhyarealcarneedsabiggersolarcellthanaminiaturecar.Solarenergycanbeusedtoheatwater,generateelectricity,movethings,orevenmakelivingthingsgrow.SinceitisplenCful,anditdoesnotcreatepolluCon,solarenergyisanexcellentenergyresource.YoumaywanttolearnmoreaboutsolarenergyontheInternet.
�108
Lesson10–Whatistheoppositeofwhitelight?Lesson10.1–Mixingoflightwithprojectors
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillexplorelightandcoloranddifferentcolorsoflightinordertoanswertheDrivingQuesCon.
ProcedureToday,youwillexplorelightandcolorusingprojectorsorflashlights.ItisimportanttomakecarefulobservaConsduringeachstepoftheinvesCgaCon.Explainwhythescreenlooksbrighterwhenaprojector(orflashlight)isshiningonitthanwhenitisturnedoff.Itisnotenoughtosaythatmorelightisshiningonit.Usethelightmodeltoexplaintheamountoflightreachingthescreenandyoureyes.(Youmayalsodrawthemodelifthatwouldbehelpful.)
Whatdoyouseeonthescreenwhenaredfilterisplacedontheflashlightortheprojectorprojectsredlight?
Predictwhatcoloroflightyouwillseeonthescreenwhenyourteacheraimsthreeprojectorsorthreeflashlights(red,green,andblue)sothattheirsquaresorcirclesareoverlapping.
�109
Conclusion
1. Explainwhyyousawthecoloryoudidwhenallthreecolorsoflightwereoverlapping.
2. Whenyoumixdifferentcolorsoflight,thenewcoloryouseeisbrighterthantheoriginalcolorsyoumixed.Explainwhythishappens.
�110
Lesson10.2–Mixingcolorsoflightonacomputer
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillusetechnologytoinvesCgatehowmuchred,green,andbluelightshouldbemixedtocreatewhite,black,andshadesofgray.
ProcedureGotothefollowingwebsite:hLp://www.exploratorium.edu/exhibits/mix_n_match/(ordoawebsearchfor“Exploratoriummixnmatch”.NoteyouwillneedtobeabletorunShockwaveonyourcomputer,anditwillnotrunonaniPad).ClickonMix-n-Match.ReadtheinstrucConsonthewebsiteabouthowtoinvesCgatemakingdifferentcolorsbycombiningred,green,andbluelight.Makesureeachstudentinyourgrouphasatleastoneopportunitytooperatethecomputer’smouse.StudentswhoarenotoperaCngthemouseshouldmakesuggesConsabouthowtogetthedesiredcolor.InvesCgatewhitelight.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtocreatewhitelight?RecordyourpredicConsbeforeyoutryit.
ManipulatethecomputerunClyousucceedinmakingwhitelight.Recordyourresults.
WhydoyouthinkthisparCcularcombinaConmakeswhitelight?
InvesCgateblacklight.a.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtocreateblacklight?RecordyourpredicConbeforeyoutryit.
�111
ManipulatethecomputerunClyousucceedinmakingblacklight.Recordyourresults.
WhydoyouthinkthisparCcularcombinaConmakesblack?.
InvesCgaCnggraylight.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtoobtaingraylight?RecordyourpredicConbeforeyoutryit.
ManipulatethecomputerunClyousucceedinmakinglightgraylightanddarkgraylight.Howmuchred,green,andbluelightdoyouthinkneedtobemixedtoobtainlightgraylight?Howmuchisneededtoobtaindarkgraylight?
WhydoyouthinktheseparCcularcombinaConsmadetheseshadesofgray?
Conclusion
1. Computerscanonlyemitred,green,andbluelight.Yet,yourcomputerscreenshowsapicturewithgreengrass,abluesky,ayellowsun,andabrownhouse.Howdoyouthinkthescreenmakesthesedifferentcolors?
�112
Lesson10.3–Howdocolorsensorswork?
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewilllearnhowtheeyeanddigitalcamerasdetectdifferentcolorsoflight.Wewillalsolearnwhymixturesofcolorsoflightappeartooureyestobenewcolors.
ProcedureLookattheimagesthatdescribethestructureoftwothings:thehumaneyeandadigitalcamera.Usethespaceprovidedtotakenotes.
Adigitalcameraisliketheeye—atitsbackisadevicecalledaCCDthathasthreedifferenttypesofcellsthatdetectred,green,andbluelight.
WhatarethetwotypesofcellsinthereCnaofaneye?
Eachtypeofconecelldetectsadifferentcoloroflight.WhatarethethreecolorsoflighttheconecellsinthereCnaaresensiCveto?
Whenyouareinadark,butnotcompletelydarkroom,itisimpossibletodetectthecolorsofobjectsintheroom.Everythingseemstobedifferentshadesofgray.Explainwhyyoucanonlyseeshadesofgray.
HowisthedesignoftheCCDofadigitalcamerasimilartothereCnaofthehumaneye?
�113
Youhavelearnedthattheeyeisalightsensor.AnswerthesequesConsabouttheeye:
Howdolightraysentertheeyewhileseeing?
Whydoesthepupilopenwideinthedarkandnarrowdowninbrightlight?
Whydoesthepupillookblack?
Conclusion
1. Whenamixtureofredandgreenlightentersyoureyes,youperceivethemixtureasyellowlight.Explainwhyyoureyeperceivesthismixtureofredandgreenlightasyellow.
�114
Reading10.4–Makingcolorphotographs
Ge`ngReadyHaveyoueverseenablackandwhitemovie?Didyoueverwonderwhyoldmovieswerealwaysinblackandwhiteinsteadofincolor?ATerall,everythinginthemoviewasactuallycolored.Today,youwillreadabouthowcamerasmakepicturesincolor.Whatyoulearnedinclassaboutcolormixingcanhelpyouthinkaboutmoviesandaboutphotographs.WhatHappensWhenIMixColorsofLight?Inclass,youlearnedhowtheeyedetectscolors.Youalsolearnedthattwothingshappenwhenyoumixedcolorsoflight.First,whenyoumixedcolors,youendedupwithanewcolor.Usingtwosources,youmixedredlightwithgreenlightandgotyellow.Whenyouaddedbluelightfromathirdsource,yougotwhite.Second,whenyoumixedcolorsfromtwosources,thenewcolorwasbrighter.Thecolorinthearealitbyallthreesourceswasthebrightestofallthecolors.YoumightalsohaveusedacomputersimulaConontheInternettoseethatwhenevertwocolorsoflightaremixed,thenewcolorisbrighterthantheoldones.Thishappensbecauseasyouincreasedtheamountoflight,morelightwasavailabletoreachyoureyes.OntheInternet,ifyouseeasimulaConabout“mixinglight”or“mixingcolorsoflight,”youwillseethatwhenyoumixmaximumamountsofred,green,andbluelight,youseewhite.Ontheotherhand,whenyoumixnored,green,orbluelight,youseeblack.TheseacCviCeshelpyoulearnthatwhitelightisthebrightestofallcolors,anditisamixtureofmanycolors.Whenyouseeblack,itmeansthatthereisnolightpresent.Whydoyouthinkashadowisblack?
HowDoPeopleSeeDifferentColors?InthepreviousacCvity,youlearnedhowpeopleseedifferentcolors.ThereCna,inthebackoftheeye,containscellsthataresensiCvetolight.TwokindsofcellsareinthereCna:cone-shapedcellsandrod-shapedcells.Therod-shapedcellstellyouhowbrightorhowdarksomethingis.Thethreedifferentkindsofcone-shapedcellsareeachsensiCvetoadifferentcoloroflight.SomearesensiCvetoredlight,sometogreenlight,andsometobluelight.Allthesecellssendsignalstoyourbrain.Yourbrainprocessesthesesignalsasimages.InLesson9,youlearnedaboutdigitalcamerasandfoundoutthattheyworkmuchlikeyoureyes—theydetectthelightcomingintothem.Somecamerasusefilminstead.Cameraswithfilmalsodetectthelightcomingintothecameraandtothefilmtorecordit.Youmayhavetakenpicturesonacamerathatusesfilm.Onceyouhaveusedupyourfilm,youhavetotakeittoastoretobe
�115
developed.Onlythencanyouseethepicturesthatyoutook.
HowDoesFilminaCameraRecordDifferentColorsofLight?Justlikeyoureyes,acamerahasaholethatletslightinside.Inyoureye,thisholeisyourpupil.Inacamera,thisholeistheshuLer.WhenyoupressthebuLontotakeapicture,youopentheshuLer.Inasplitsecond,lightentersthecameraandtravelsthroughit.ThelightreachesthebackofthecamerawheretheCCDislocated.Inacamerathatusesfilm,thisiswherethefilmislocated.Thefilmabsorbslightwhichcausesittochangecolor.Redlightcausesthefilmtochangeinadifferentwaythanbluelight.Inblackandwhitefilm,allcolorsoflightwillcausethefilmtochangeinthesameway.Insteadofproducingareaswithdifferentcolors,blackandwhitefilmonlyproducesareasthatarelighterordarker.Colorfilmismadeofthreelayers.TheselayersoffilmareliketheconecellsinthereCnaofaneye.Somelayerssenseredlight,othersgreenlight,andothersbluelight.ThedifferenceisthatinthereCna,thedifferentconecellsarelocatedsidebyside,andinfilmthedifferentlayersareoneundertheother.Ifcolorfilmishitbyredlight,thelayerthatissensiCvetoredlightdoesnotbecomered—itbecomeslightblue.GreenlightmakesthelayersensiCvetogreenlightbecomelightpurple.BluelightmakesthelayersensiCvetobluelightbecomeyellow.SoifyoulookatfilmaTerithasbeenexposedtolight,whatyouwillseewilllookverydifferentfromtheobjectthatyoutookapictureof.Itwillhavethesameshape,butallthecolorswillbewrong.Thisphotoshowswhatfilmwouldlooklikeifyoutookaphotoofacastle.ItisinteresCngtolookatthenegaCvesfromfilmthathasbeendevelopedtoseethedifferencebetweenthenegaCvesandthephotos!ATerphotoshavebeentaken,filmneedstobeprotectedsoitwillnotgetexposedtoanymorelight.FilmcansCllabsorbmorelight.Ifmorelightweretostrikethefilm,itwouldrecordthislightaswellasthelightthathititwhiletakingthepictures.Thiswouldmessupthefirstpictureitrecorded.Thefilmisrolledandplacedintoacanisterthatdoesnotletinanymorelight.ThepersonwhodevelopsthefilmopensthecanisterincompletedarknessandputsthefilmintoaliquidthatmakesthefilmnolongersensiCvetolight.Thefilmcanthenbetakenoutintotheopenwithoutanyworryofmessingitup.Thestorethenusesthefilmtoprintphotos.Themachinethatprintspicturesonfilmchangesthecolorsonthefilmbacktotheoriginalcolors,sothephotoslookliketheoriginalobjects.2.Whydoyouthinkthereisaneedforthreelayersinafilm?
3.Whydoyouthinkthelayersinthefilmneedtobetransparenttoallcolorsotherthantheoneitabsorbs?
�116
HowDoesaTelevisionShowColors?Sometelevisionshave“guns”nearthebackthatsendCnyparCclescalledelectronstowardthescreen.Magnetsinsidethetelevisioncanpushorpulltheelectronsup,down,leT,orright,sothattheycanhitthescreenanyplace.Theinsidesurfaceofatelevisionscreeniscoatedwithverysmalldots.Whenanelectronhitsadot,itmakesaweakflashoflight.Therearethreedifferentkindsofdots,andeachonegeneratesadifferentcoloroflight.Bycontrollingwhichdotsarehitbyelectrons,someonecancontrolwhichcolorsoflightaremadebythescreenateachpointonthescreen.AsyoulearnedinLesson9,youreyesperceivedifferentmixturesofred,green,andbluelightasnewcolors.Sincethedotsonthescreenmakingthelightaresosmall,youcannottellthemapart.WhentwodotsnexttoeachotherlightupatthesameCme,youseeonlyoneflashoflight.Thecolorofthatlightwilldependuponthecolorsoflightmadebythedots.Youhavelearnedhowcamerafilmandtelevisionscombineonlythreecolorsoflighttomakeallthecolorsthatyoureyecansee.Forexample,youknowthatredandgreenlightcanmixtomakeyellowlight.ThinkofitnextCmeyouseesomethingyellowlikeaflower.Areyouactuallyseeingyellowlight,orisitamixtureofredandgreenlightthatlooksyellowtoyoureyes?Inthenextlesson,youwilllearnhowyoucantellwhetheryouareseeingapurecolororamixtureofdifferentcolorsoflight.
�117
Lesson11–Howdoobjectschangethecoloroflight?Lesson11.1–AnalyzingcolorcomposiAon
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewilllearnhowtoanalyzelighttodetermineoutofwhichothercolorsoflightitiscomposed.
ProcedureYourteacherwillprojectawhitelineonthescreen.Explainwhythelineappearstobewhite.
WhenyourteachercoverstheprojectorwithapieceofC-Spectra,twocolorfulimagesarecreated.Eachimagecontainsallthecolorsoftherainbow.Makealistofthecolorsthatyousee.
Explainhowyouthinkdifferentcoloredobjectsthatdonottransmitlight,likeaballoratable,colorthelightthattheyscaLerorreflect.Drawamodelifithelpsyou.
UsingapieceofC-Spectra,onepersoninyourgroupshouldlookatthecoloredlineonthesheetofblackpaperthatyourteachertapestotheboard.Thispersonshouldcheckinthetablethecolorsthattheycansee.Then,whentheteachertapesadifferentsheettotheboard,adifferentstudentshouldanalyzethenewline.Everypersoninyourgroupshouldhavetheopportunitytoanalyzeatleastoneline.
ColorsofLight
Red Orange Yellow Green Blue Violet
Red Line
Orange Line
Yellow Line
Green Line
Blue Line
Violet Line
�118
ExplainwhyyouthinkthedifferentcoloredlinesscaLerdifferentcolorsoflight.
Whydoyouthinkthecoloredlineswereprintedonblackpaperratherthanonwhitepaper?
Conclusion
1. Whatcolordoyouthinkyouwouldhaveseeniftheredstripehadbeenilluminatedbyredlight?Explainyourideas.
2. Whatcolordoyouthinkyouwouldhaveseeniftheredstripehadbeenilluminatedbygreenlight?Explainyourideas.
�119
Reading11.2–Rainbows
Ge`ngReadyHaveyoueverwonderedwhyrainbowsappear?YouhaveprobablynoCcedthatrainbowshavesomethingtodowiththeweather.Youhaveprobablythoughtaboutthefactthatthewordrainbowhasraininit,andthatiswhenyouseerainbows.However,youdonotseearainboweveryCmeitrains.Thisreadingisaboutwhatmakesrainbowsappearinthesky.ThinkofaCmewhenyouhaveseenarainbow.TrytorememberwhattheweatherwaslikeattheCme.ThesethreequesConsmighthelpyou:
• WasitsCllrainingorhadtherainstopped?
• Wasthewholeskycloudy?
• Wasitduringthedayornight?YouCanMakeYourOwnRainbowBeforereading,hereisanacCvityyoucandotocreateyourownrainbow.Youneedtodothisonasunnyday.First,findawindowwherethesunisshiningin.Second,pullatableclosetothewindow.Third,placeafullglassofwaterontheedgeofthetablewherethesunisshiningthebrightest.Lookatthefollowingdiagramtoseehowtosetupyourexperiment.Onceyouplacetheglassonthetable,lookatthefloorneartheglass.Youshouldseearainbowonthefloor.Ifitisnotasunnyday,youcansClltrytomakeyourownrainbow.Makearoomasdarkaspossibleandsetupafullglassofwaterontheedgeofatable.Insteadofsunlight,youneedaflashlight.Turnontheflashlightandpointitattheglass,asiftheflashlightwerethesun.Keeptheflashlightpointedattheglass,butmovetheflashlightaliLleataCmeunClyouseearainbowonthefloororonthewall.Inthislesson,youwilllearnhowdropsofwaterandsunlightworktogethertoformrainbows.InLesson9,youlearnedthatwhitelightisamixtureofallthedifferentcolorsoflightthatyoucansee.Red,orange,yellow,green,blue,indigo,andviolet(ROYGBIV)canallbefoundinwhitelight.However,whenyouseewhitelight,youdonotusuallyseethosecolors.Inordertobeabletoseeallthecolorsthatmakeupwhitelight,youwouldhavetobreakwhitelightapartintoitscolorcomponents.ThatiswhatyoudidinLesson10,usingC-Spectra.UsingaPrismAprismisanotherwaytobreakwhitelightintoitscolorcomponents.AprismisatriangularpieceoftransparentglassorplasCc.Abeamofwhitelightshiningononesideoftheprismwillcomeoutontheothersidebrokenupintoitscolorcomponents.Thisfigureshowshowwhitelightenteringtheprismcomesoutintheformofarainbow.Nowyouknowthataprismseparateswhitelightintocolorsandyouknowthatthecolorslooklikearainbow.YousClldonotknowhowarainbowisformed.Whenlightentersaprism,theprismcausesthelighttobendveryslightlyortochangedirecConsjustaliLlebit.ThisbendingiscalledrefracCon.Notalllightgetsbentinthesameway.Somecolorsoflightgetbentmorethanothers.Thecoloroflightthatgetsbentthemostisblue,whilethecoloroflightthatgetsbenttheleastisred.Lookagainatthefigureoflightbeingrefractedbyaprism.Canyouseethatbluegetsbentmorethanred?Becausethedifferentcolorsoflightbenddifferently,theycomeoutoftheprismatdifferentplacesandmoveoutofitindifferentdirecCons.BecausetheymoveindifferentdirecCons,theyspreadawayfromeachother.Thatiswhyyoucanseethemseparately—thecolorsarenolongermixedtogether.Whatyouseeisanareainwhichthecoloroflightchangesgraduallyfromonetoanother.Itlooksjustlikearainbow.
�120
HowAreRealRainbowsFormed?
Inarealrainbow,raindropsintheairactlikeverysmallprisms.Lightenterstheraindropsandgetsbentbythem.Eachcoloroflightisbentslightlydifferently.Somecolorsgetbentabitmore;othersgetbentabitless.However,unliketheprism,wherethelightcomesinonesideandleavesonanother,thelightenteringaraindropisreflectedbackatthefarsideoftheraindrop.Lookthedrawing.Thelightreturnstothesamesideoftheraindropitenteredfrom,andthenitexits.ThelightthatleavestheraindropmovesinmanydifferentdirecCons,andeachcolormovesinapredictabledirecCon.RefracConbreaksthelightenteringtheraindropintocolorcomponents,justlikeintheprism.TherefracConofthelightbytheraindropscausesthecolorstospreadouttocreateasemicircleofcolorinthesky,orarainbow.HaveyounoCcedthatthesunisalwaysbehindyouwhenyoulookatarainbow?Thinkaboutthemodeloflightthatyoudevelopedinclasstohelpyouexplainwhythesunmustbebehindyouforyoutoseearainbow.ASpecialPhenomenon:DoubleRainbowsPerhapsyouhaveseenadoublerainbowlikeinthisphoto.Thebrighterrainbowiscalledtheprimaryrainbow.Thefainterrainbowiscalledthesecondaryrainbow.Thesecondaryrainbowismadewhenlightisreflectedtwiceinsidetheraindrop.BecauseofthedoublereflecCon,thelightleavestheraindropatadifferentangle,soyouseethesecondaryrainbowhigherup.Ifyoulookcloselyatthepicture,youwillalsonoCcethatthecolorsofthesecondaryrainbowareintheoppositeorderofthecolorsintheprimaryrainbow.ThedropsofrainhavetobejusttherightsizetocreatetworeflecCons.ThisdoesnothappenveryoTen,sodoublerainbowsareararesighttosee.Howcouldyouexplainhowrainbowsareformedtosomeonewhoisnotinyourscienceclass?Forexample,howcouldyouexplainrainbowstosomeoneathome?Orhowcouldyouexplainrainbowstosomeoneyoungerthanyou?Thinkaboutthatpersonasyouraudience,andexplainhowrainbowsareformedinawaythatpersonwouldunderstand.Youmightfindithelpfultodrawamodeltoexplain.
�121
Reading11.3–LunarEclipses
Ge`ngReadyEverydaythesunappearstoriseintheeast,goacrossthesky,andthensetinthewest.Everymonththemoongoesthroughitsphasesfromnewmoontofullmoonandbackagain.ItallseemssoorderedunClsomethingunexpectedhappens.OnenightthemoonrisesfullandbeauCful,butthen,withinafewminutes,itstartstochange;itgetsdarkeranddarker,unClitdisappears.Thenitturnsred.Alunareclipseoccurs.OurancestorswereinCmidatedbythesightofalunareclipse.Theycouldnotunderstandwhatwashappening—theyfearedtheendoftheworldwascoming.Theyprayedandbeggedforthemoontoreturn.Today,thankstoadvancesinscienCficknowledge,weknowwhatcausesalunareclipseandwecanenjoyitsbeauty,knowingitisanaturalphenomenonwhichdoesnotcauseanyharm.Inthisreading,youwilllearnaboutlunareclipses:why,when,andhowtheyhappen.Earth’sShadowAlunareclipsetakesplacewhenthereisafullmoon.YoulearnedbeforethatafullmoonexistswhenEarthisbetweenthesunandthemoon.Ifyoulookcloselyagainatthemodelshowingthephaseofafullmoon,youwillnoCcesomethingthatdoesnotmakesense.Ifthesun,theearth,andthemoonareallalignedandthemoonisexactlybehindEarth,howdoesthemoongetlitbythesun?Shadowsareactuallydarkareascausedbyanobjectblockinglight.Earthisanobjectthatblocksthesun’slight;thereforethereisashadowedareabehindEarth.Whydoestheearthnotalwaysblockthesun’slightfromreachingthemoon?IsthemoonnotinEarth’sshadow?ThetruthisthateveryonceinawhileEarthdoesblockthesun’slightfromreachingthemoon,andthisiswhatcausesalunareclipse.HowoTendoyouthinkalunareclipseoccurs?Explain.
LunareclipsescanonlyhappenwhenthemoonisfullanditpassesbehindEarthandintoitsshadow.Ifwehaveafullmoononceeverymonth,thenweshouldalsohavealunareclipseonceeverymonth.ThisthoughtmakessenseifyouthinkofEarth’sorbitandthemoon’sorbitsasbeinginthesameplane.However,themoon’sorbitisinclinedaboutfivedegreestoEarth’sorbit.Lookatthisimagecarefully.
�122
ThatmeansthatmostoftheCme,duringfullmoon,themoonpassesaboveorbelowEarth’sshadowandmissesitenCrely.Noeclipsetakesplace.Onlyonceortwiceayear,onaverage,doesthemoonpassthroughsomeporConofEarth’sshadow,causinganeclipsetooccur.ImagineyouareanastronautstandingonthemoonduringatotallunareclipseandwatchingEarth.Whatwouldyousee?
Ifduringafullmoon,thesun,theearth,andthemoonareallonebehindtheother,howdoesEarthnotblockthesun’slightfromreachingthemoon?
TypesofEclipsesWhenthemoonisinEarth’sshadow,nolightfromthesunreachesit,andthus,eventhoughitisintheposiConofafullmoon,itisnotilluminatedandcannotbeseen.BecausethemoonisinconstantmoConaroundEarth,itgraduallyenterstheshadowedarea—slowlydisappearingunClitcannotbeseenatall.Thenasitkeepsmoving,itgraduallyleavestheshadowedarea,enteringtheareawheresunlightcanreachitagain—slowlyreappearing.Thesechanges—frombrightnesstodarknessandbackagainintobrightness—cantakeuptofourhours.Sincethesunisalargelightsource,itcreatesshadowsthathavefullydarkareasandparCallydarkareas.Forthisreason,theshadowofEarthisactuallycomposedoftwoareas.Lookatthemodel.TheouterpartsoftheshadowaretheparCalshadow—areaswhereEarthblockspartbutnotallofthesun’srays.Incontrast,theinnerpartoftheshadowisacompleteshadowwhereEarthblocksalldirectsunlight.
�123
Lookatthemodel.InwhichposiConsisthemoon(A,B,C,D,E,F,orG)fullyshadowed?InwhichposiConorposiConsisitparCallyshadowed?Explain.
Therearethreetypesoflunareclipse:1. WhentheenCremoonisinthefullyshadowedarea,itisfullydarkened.Thisiscalledatotal
lunareclipse.2. Whenonlypartofthemoonisinthefullyshadowedarea,aparCallunareclipseoccurs—partof
themoonisdarkandtheotherpartisparCallyilluminated.3. WhenthemooniscompletelyintheparCallyshadowedarea,itissCllsomewhatlighted.Itis
difficulttonoCceanychangewiththenakedeye.Weneedprofessionaltelescopestoobservethechangesinthiskindofeclipse.
Followingarephotosofthemoonindifferenttypesofeclipses.Pleasewritebeneatheachonewhetheritisatotaleclipse,aparCaleclipse,ornoeclipse.AlsowritewhichposiConofthemooninthepreviousmodel(A,B.C,D,E,F,orG)fitseachphoto.
�124
WhyDoestheMoonTurnRedduringaTotalLunarEclipse?AveryspecialfeatureofthetotallunareclipseisthataTerthemoonhasgonedark,itturnsred.(YoumightwanttowatchaneclipsevideoandpayspecialaLenContothat.)ThereddishcolorisaresultofindirectlighCngofthemoon.WhilethemooniscompletelywithinEarth’sshadow,indirectsunlightsCllmanagestoreachandlightit.ThissunlightpassesthroughtheEarth’satmosphere.Then,itoTenchangesdirecConbybouncingoffthegasmoleculesintheair.Someofthislightreachesthemoon.TheEarth’satmosphereactslikeafilter,absorbingmanycolors.Theremaininglightiscoloredreddish-orange.Itismuchdimmerthanoriginalwhitesunlight.Thislightreachesthemoonandmakesitappearred.TheexactcolorandbrightnessofthelightreachingthemoonduringaneclipsedependsonthehowmuchdustisinEarth’satmosphere.ATeravolcanicerupCon,forexample,atotaleclipseisverydarkbecausethereisalotofvolcanicashinEarth’satmosphere.DuringthetotallunareclipseofDecember1992,themoonwasnearlyinvisiblebecauseofdustfromavolcanothateruptedinthePhilippines.Inthisreading,youlearnedwhatcausesalunareclipseandwhatkindsofeclipsesthereare.Yousawthatevenanamazingevent,suchasalunareclipse,canbeexplainedbyafewscienCficideasyoualreadyknow.Thisisanexampleofthepowerofscience.Asmallnumberofideascanexplainalargevarietyofphenomena!
�125
�126
Reading11.4–DiffracAon
AdiffracCongraCngisaseriesofequallyspaced,microscopic,paralleldarklineswithatransparentareabetweenthem,somethinglikewhat’sshowninFigure1onlymuch,muchsmaller.WhenlightreachesadiffracCongraCng,itisabsorbedatthedarklinesandtransmiLedatthetransparentareas.Thus,whiletherewasaconCnuousareaoflightbeforethediffracCongraCng,aTerittherearethousandsofindependentmicroscopicsourcesoflight.Fromthesemicroscopicsources,lightspreadsoutforwardinalldirecCons.SeeFigure2.ScienCstssaythatthelighthasbeendiffracted.
ThediffractedlighttravelsforwardandspreadsoutunClitreachedascreen.BecausethelightfromeachmicroscopicsourceonthediffracCongraCngtraveledforwardinalldirecCons,eachpointonthescreenisilluminatedbylightfrommany,ifnotall,ofthesourcesonthediffracCongraCng.UndercertaincondiCons,raysoflightcancanceleachotherout.Imagineanobjectbeingpulledonbothsidesbysprings.Ifthespringspullequally,theobjectwillnotmove,eventhougheachspringindependentlywouldhavemovedtheobject.Somethinglikethatcanhappenwithlight,eventhoughlightdefinitelydoesnotpushorpullthescreen.ThelightcomingfromthediffracCongraCngissetupsothatexceptforafewspots,thevariouscolorsoflightcancelthemselvesoutalmosteveryplaceonthescreen.ThatiswhyyougetseveralredspotsseparatedbyblanknesswhenyoushinearedlaserthroughadiffracCongraCng.Differentcolorsoflightwillremainintactatdifferentplacesonthescreen.Thuswhenyoushinewhitelight,whichisacombinaConofmanycolorsoflight,yougetareaswhereredlightremains(butnoothercolor),areaswheregreenremains(butnoothercolor),andsoon.Inthisway,youcanseeallthedifferentcolorsthatmadeupthewhitelight.
�127
�128
Reading11.5–SolarEclipses
Ge`ngReadyIfyouthinkalunareclipseisanawesomeevent,asolareclipse(aneclipseofthesun)isevenmoreawesome.Inthemiddleoftheday,theskyslowlybecomesdarkasthesundisappears,leavingonlyahalooflightinthesky.AsolareclipseoccurswhenthemoonpassesbetweenthesunandEarthsothatthesunisallorpartlyblockedbythemoon.Somepeopleconsiderasolareclipsetobeoneofthemostamazingeventsinnature.Manypeopletravellongdistancestoobserveone.TheInternetisagoodsourceforphotosandvideosofsolareclipses.Accordingtowhatyoulearnedaboutphasesofthemoon,inwhichphasedoyouthinkasolareclipsecanoccur?Explainyourideas.Ifyouarenotsure,youmightwanttogobacktoReading10.2aboutphasesofthemoon.
AsolareclipsecanonlytakeplacewhenthemoonpassesbetweentheEarthandsun.Ifthemoon’sshadowhappenstofallsomewhereonEarth’ssurface,fromthatplacepeoplecanseesomepartofthesunbeingcoveredoreclipsedbythemoon.Asyoucanseeinthemodel,asolareclipsemaybeseenfromonlyasmallareaonEarth.Onlypeopleintheregionwherethemoon’sshadowfallswillbeabletoseeit.Whydoesthemoon’sshadownotcoverallofEarth?
ThereisevidencethatthemoonisveryslowlygecngfartherandfartherfromEarth.AssumingthedistancebetweenEarthandthesundoesnotchange,howwillthisaffectthesizeoftheshadowonEarthcausedbysolareclipses?Drawamodelofasolareclipsetohelpyouexplainyouranswer.YoumaywanttorecalltheinvesCgaConyoudidwithshadowsinLesson5.
�129
AsolareclipsemaybetotalorparCal,dependingonhowmuchofthesunisblocked.TwotofiveparCalsolareclipsesoccureachyearonEarth.Atotaleclipseoccursonlyonceeveryeighteenmonths.EachtotaleclipseisonlyvisiblefromaverysmallareaonEarth,wherethesunisinthefullshadowofthemoon.Therefore,itisraretoseeatotaleclipseatyourhouseoryourschool.Youwouldhavetowaitabout375yearstoseetwototalsolareclipsesfromthesameplaceonEarth.UsetheInternettofindoutwhenandwherethenexttotalsolareclipsewilloccur.Usewhatyoulearnedinthereadingaboutlunareclipsestoexplainwhythereisnotasolareclipseonceeverymonthwhenanewmoonphasetakesplace.Inthisphoto,youcanseeasolareclipseinwhichthesunappearsasaverybrightringsurroundingtheoutlineofthemoon.ManysolareclipseslooklikethisbecausesomeCmesthemoonlookstoosmalltoblocktheenCresun.ThereasonwhythemoonsomeCmesappearstoosmalltocoverthesunhastodowiththemoon’sorbitaroundEarth.Thatorbitisnotperfectlyroundbutisshapedlikeaslightoval.AsthemoonorbitsEarth,itsdistancefromtheearthvaries.SomeCmesthemoonisclosertoEarth,andsomeCmesitisaliLlefarther.Therefore,themoon’ssizeseemstovary.WhenitisfartherfromEarth,itlookssmaller.IfaneclipseoccursatthatCme,itistoosmalltocompletelycoverthesun,andyoucanseethebrightringofthesunbehindthemoon.However,ifaneclipseoccurswhilethemoonisclosertoEarth,themoonappearslargeenoughtocoverthewholesun.
SummaryUsethetabletocomparealunareclipseandsolareclipse..
Lunar Eclipse Solar Eclipse
What do we see from earth?
What phase is the moon?
Relative location of earth sun and moon
How much of the earth gets to see this eclipse?
Total or partial?
How often does this occur?
�130
Lesson12–InfraredLightandtheWaveModelLesson12.1–Whatisleavingaremotecontrol?
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillexplorehowaremotecontrolworkstoexplorewhetherthereislightwecannotsee.
PredicAon:
Doyouthinkthataremotecontrolproduceslight?Explainwhyorwhynot.
Data
Action with remote Describe what happens when your teacher does the action with the remote
Points at you and presses the on/off button
Points at a TV or projector and presses the on/off button.
Points at a digital camera or a doc cam and presses the on/off button
Puts a piece of cardboard between the remote and the TV/projector when pressing button
Points the remote towards a mirror while pressing the button
Puts a piece of clear plastic or glass between the remote and the TV/projector
�131
Conclusion
1. Didyourresultssupporttheideathattheremoteisgivingofflight?Whyorwhynot?
2. Explainwhyyougotasimilarresultusingaremoteandusingaflashlight.(Hint:YoumaywanttoremembertheearlierlessonwhereyouusedvisiblelightinsteadofIR.)
3. Touseyourunderstandingevenmore,explaintosomeoneathomehowaremotecontrolworks.
4. Isanyofthelightfromtheremoteabsorbed?DesignaninvesCgaConyoucoulddotofigureouttheanswertothisquesCon.Describeordraw(orboth)howyouwouldtestwhetheranyIRlightisabsorbed.(Hint:LookbacktoLesson8toremindyourselfofhowyoudeterminedthatlightcouldbeabsorbed.)
5. MakeapredicCon.IftheremoteweregivingofflightandyoudidthedemonstraConyoudescribed,whatwouldyouexpecttohappen?Why?
�132
Reading12.2–InfraredLight
Ge`ngReadyYoudonothavetotouchafiretoknowitishot.Youcanseeitglowing,andyoucanfeelthatitishot.Haveyoueverfeltsomethingelsethatwashoteventhoughitwasnotglowingandyoudidnottouchit?ThinkofsomethingthatfitsthisdescripCon.Describewhattheobjectwasandhowcloseyouweretobeabletofeelthatitwashot.Asyouread,youwilllearnmoreaboutsomethingcalledinfraredlight.Infrared(IR)lightiswhyyouperceiveflamesashot!Bytheendofthisreading,youwillbeabletonameafewwaysthatpeopleusetheirunderstandingofinfraredlightoutsideofscienceclass.WhyArethereDifferentColorsofLightinaFlame?Acampfiregivesofflotsoflight.Whenyoulookatacampfire,mostoftheflameslookyellow.ButhaveyouevernoCcedthattherearedifferentcolorsinafire?Lookatthephotoofamatch.TheboLomoftheflameisblue,themiddleisreddish,andthetoplooksyellow.Inclass,youlearnedthatthewavelengthoflightdetermineswhatcoloryousee.Lightismadeofwaves,andthedistancebetweenanytwoconsecuCvewavesiscalledwavelength.Differentwavelengthsoflightcreatedifferentresponsesinyoureyes.Ifashortwavelengthofvisiblelightreachesyoureye,youreyerespondsbysendingacertainsignaltoyourbrain.Yourbrainreceivesthissignalandinterpretsitasblue.Ifalongwavelengthofvisiblelightreachesyoureye,youreyerespondsbysendingadifferentsignaltoyourbrain.Yourbraininterpretsthissignalasred.Iflighthasanevenlongerwavelengththanredlight,itdoesnotcreatearesponseinyoureye,becauseyoureyeisnotsensiCvetowavelengthsthatarelongerthanthoseofredlight.Becauseyoureyedoesnotrespondtothislight,itiscallednonvisiblelight.Nonvisiblelightwithawavelengththatislongerthanredlightiscalledinfraredlight.Whileacampfiregivesoffdifferentcolorsofvisiblelight,itgivesoffnonvisibleinfraredlight,too.Ofcourse,youcannotseeit!WhatMakesaFlameFeelHot?Eventhoughyoureyescannotdetecttheinfraredlightgivenoffbyafire,yourskincan.Wheninfraredlightreachesyourskin,yourskinabsorbsit.Thisabsorbedlightcausesthetemperatureofyourskintoincrease.Then,nervesinyourskinsendasignaltoyourbrainthatyourbraininterpretsashot.Acampfirecanfeelhotfrom10feetawaybecauseitgivesoffinfraredlightthatyourskindetects.SomeCmesobjectscangiveoffinfraredlightwithoutgivingoffanyvisiblelight.Astoveinyourhousemaylooknormaltoacamerathatdetectsonlyvisiblelight,butacamerathatdetectsinfraredlightcanshowadifferentpicture.Comparethesetwophotos.ThephotoontheleTwastakenwitharegularcamera.Youreyecannottellwhichburneronthestoveishotbecauseyoureyecannotseeinfraredlight.However,ifyouheldyourhandneareachburner,youcouldtellwhichonewashot,becauseyourskinwouldabsorbtheinfraredlightandsendasignaltoyourbrain.Thephotoontherightwastakenwithaninfraredcamera.Thecameraletsyoureyeseewhichburnerishot.HowDoesThisRelatetotheRemoteControlAcAvityWeDidinClass?Inclass,youusedaremotecontroltosendasignaltoatelevisionset.Then,youlookedattheremotecontrolwithadigitalcameraandsawsomethingflashingthatyoucouldnotseewithyoureyes.Howdidyourclassdeterminewhetherthesignalsentbytheremotecontrolwaslight?Explainwhythetestsyourclassdidhelpedyoudecidewhetherthesignalwaslight.
�133
Inclass,youdeterminedthatthesignalsentbyaremotecontrolwasakindoflightthatyoucannotsee.Younowknowthatthislightiscalledinfraredlight.Theinfraredlightofacampfire,amatch,andaburneronyourstovefeelshot.Whydoesitnotfeelhotwhenyoupointaremotecontrolatyourskin?Aremotecontrolgivesoffasmallamountofinfraredlight.Theamountissosmallthatitdoesnotheatyourskinenoughtosendasignaltoyourbrainthatitfeelshot.ButitisenoughlighttobedetectedbyaTV.HowDidPeopleNoAceInfraredLightintheFirstPlace?Youusedaremotecontroltostudyinfraredlightinclass,butthefirstpersontodiscoverinfraredlightdiditlongbeforeremotecontrolswereinvented.ThefirstpersontodiscoverinfraredlightwasSirFrederickWilliamHerschel.Heusedaprismtoseparatesunlightintoitscolors,justlikeyoudidinclasswithC-Spectra.Heknewthatlightcouldbeabsorbedbyobjectsandmakethemheatup.Hewantedtoknowwhethersomecolorsoflightheatedobjectsmorethanothers.ToinvesCgatethis,heplacedthermometerswithblackenedbulbsinthedifferentcolorsofthespectrumandrecordedtheirtemperature.Lookcloselyatthefollowingphotoofthermometers.Thereadingonthethermometersincreasesasyoulookfrombluetored.ATernoCcingthis,Herschelplacedathermometerjustoutsideoftheredpartofthespectrumwheretherewasnovisiblelight.Tohissurprise,hefoundthatthisareahadthehighestreadingofall!HerealizedthattheremustbesomekindoflightheaCngupthethermometerbutthathiseyescouldnotdetectit.Thislightwasinfraredlight.UsingwhatyouknowaboutcolorsandlightabsorpCon,explainwhySirFrederickWilliamHerschelusedthermometerswithblackenedbulbsinhisexperiment.
HowDoPeopleUseInfraredLight?Eventhoughyoucannotseeit,infraredlightisveryimportant.SinceHerscheldiscoveredthatsunlightcontainsinfraredlight,astronomershavebeenusingspecialIRcamerastolookatstarsandotherobjectsinthesky.Justasahotstovelooksdifferenttoaregularcamerathantoaninfraredcamera,objectsintheskylookdifferent,too.Thispictureshowsagalaxyphotographedwitharegularcamera(leT)andwithaninfraredcamera(right).Theinfraredcamerashowspartsofthegalaxythatareinvisibletotheeyebecausetheydonotgiveoffvisiblelight.SomeinfraredgogglesworkbydetecCngtheinfraredlightthatobjectsgiveoff.OtherIRgogglesuseaninfraredflashlighttobounceinfraredlightoffofobjects.UsinganinfraredflashlightmakesobjectsappearbrightertosomeonewearingIRgoggles.IfsomeonewearingIRgogglesweretoshineaninfraredflashlightatyou,whatwouldyousee?Why?
�134
HowDoDoctorsUseInfraredLight?DoctorsalsouseinfraredlighttochecktheamountofoxygeninapaCent’sblood.Doctorsdiscoveredthatoxygen-richbloodabsorbsthemostinfraredlight,andittransmitsorscaLersvisibleredlight.Thatprobablymakessensetoyoubecauseitexplainswhyyourbloodappearsred!Ifbloodisnotoxygen-rich,ittransmitsmoreinfraredlightandlessvisibleredlight.ByshiningredandinfraredlightthroughapaCent’sfingerandmeasuringtheamountofeachtypeoflightthatcomesouttheotherside,doctorscandeterminehowmuchoxygenisintheblood.Knowinghowbloodabsorbs,transmits,orscaLerslightallowsdoctorstotestbloodwithouthavingtotakeabloodsamplefrompeople.Supposeyouwerewearingasensoronyourfinger,anditdetectedalotofinfraredlightandnotmuchvisibleredlight.Doesthismeanthatyourbloodhasalotofoxygeninit,oronlyaliLleoxygen?Why?
Inthisreading,youhavelearnedhowinfraredlightwasdiscoveredandyouhavelearnedaboutmanyusesforinfraredlight.Butinfraredlightisnottheonlykindoflightyoucannotsee.Inthenextlesson,youwilllearnaboutothertypesoflightthatyoucannotseeandhownonvisiblelightaffectsyourlifeeveryday.
�135
�136
Lesson12.3–IntroducingtheWaveModel
Whatwasthepointofthelastlesson?
Whatwillwedo?WewilldosomeacCviCestolearnmoreaboutthedifferencesbetweenvisibleandnonvisiblelight.Thenwewillreviseourmodeloflighttoaccountfornewevidence.
ProcedureAsyourteacherchangesthepitchcomingfromthecomputer,raiseyourhandwhenyoucannolongerhearthesound.Dideveryone’shandgoupatthesameCme?Why?
Aretheresoundsthatyoucannothear?Explain.
Describethewavemodelpresentedinclass.
Basedonyourunderstandingofthewavemodel,explainwhyyoureyecouldnotdetectthelightcomingfromtheremotebutthecameracould.
�137
Conclusion
1. Accordingtothewavemodeloflight,whatmakesbluelightdifferentfromgreenlight?
2. Compareredlightwiththeinfraredlightthatcomesfromtheremote.(Rememberthatcomparemeanstodescribewhatissimilarandwhatisdifferent.)
3. Describehowvisiblelightisdifferentfromnonvisiblelight.
�138
Lesson13–UltravioletLightandNonvisibleLightImageryLesson13.1–InvesAgaAngUVlight
Whatwasthepointofthelastlesson?
Whatwillwedo?WewillinvesCgateanothertypeoflightthatoureyescannotdetect:ultravioletlight.
Data
SunscreensaredesignedtoprotectyourskinfromUVlight.Predictwhatyouwillgetintheexperiment,thenmakemeasurementsandcomparetheresultswithyourpredicCons.
1. IsthepercentofUVlightblockedbythesunscreengreaterorlessthanthepercentofvisiblelightblocked?Isthissimilartowhatyoupredicted?
2. WhywouldcompanieswanttheirsunscreentoabsorbnearlyalloftheUVlightthathitsitbutnoneofthevisiblelight?
3. Whatwouldsunscreenlooklikeifitabsorbedallofthevisiblelightthathitit?
Conclusion
1. Howdoesthesunscreenworksimilartothecolorfiltersthatyouhaveusedinpreviouslessons?
Ultralight(UV) light Visable Light
Reading without sunscreen
Prediction of how much light will be blocked by the sunscreen
Actual reading with the sunscreen
Actual percent of light blocked by sunscreen
�139
�140
Reading13.2–Non-visiblelight
Ge`ngReadyImaginethatyourremotecontrolusedvisibleinsteadofnonvisiblelight.Wouldthisbeagoodidea?Why?
Today,youwillreadmoreaboutnonvisiblelight.Youprobablydonotrealizeit,butnonvisiblelightplaysanimportantroleinyourlifeeverysingleday!Bytheendofthisreading,youshouldbeabletodescribehowradios,cellphones,microwaveovens,orx-raysmachinesusenonvisiblelight.Byexplainingevenoneofthosetosomeonewhoisnotinyourclass,youcanhelpthemunderstandsomethinginteresCng.AndyouwillhelpyourselfunderstandnonvisiblelightevenbeLerbyexplainingittosomeoneelse!HowDoesLightTravel?Inclass,youlearnedthatlighttravelsinasimilarwaytowavesmovingacrosswater.Yousawthatwhenwaterwavesmoveinapanofwater,theripplescanbespacedveryclosetogether(havingasmallwavelength)orveryfarapart(havingalargewavelength).Lightcanalsotravelwithawavelengththatisverysmallorverylarge.Butyoureyescanonlydetectlightifitswavelengthiswithinacertainrange.Humaneyescanonlydetectlightwithawavelengthbetween400and700nanometers.AnanometerisonebillionCmessmallerthanameter.Howsmallisthat?Asinglehaironyourheadisabout80,000nanometerswide.ThismeansthatthewavelengthofvisiblelightismorethanahundredCmessmallerthanthewidthofyourhair!Trytothinkaboutthisbeforeyoukeepreading.YoumayneedtoreadthroughthisdescripConagaintoreallyunderstandhowsmalltherangeoflightisthatyoureyecansee.Itisamazing!HowMuchNonvisibleLightIsThere?InfraredlighthasawavelengththatisaliLlegreaterthan700nanometers.Therefore,youcannotseeit.UltravioletlighthasawavelengththatisaliLlelessthan400nanometers.
Wavelength<400nanometers=nonvisible(UV)Wavelengthbetween400–700nanometers=visibleWavelength>700nanometers=nonvisible(IR)
Eventhoughthewavelengthsofinfraredandultravioletlightcanbeclosetothewavelengthsthatyoureyescandetect,youreyessCllcannotdetectthem.NonvisiblelightcanhaveawavelengthmillionsofCmessmallerthanahumanhairorbiggerthantheenCreEarth!Becausenonvisiblelightcanhavesomanydifferentwavelengths,scienCstscreatedasystemtokeeptrackofthem.Inthissystem,scienCstshavedividedallofthepossiblewavelengthsintocategories.Youhaveprobablyheardofsomeofthecategories,becausemanyofthedevicesyouuseeverydayoperateusingnonvisiblelight.Thelongestwavelengthsoflightarecalledradiowaves.Findthemonthefollowingchart.Theshortestwavelengthsarecalledgammawaves.Findthemonthechart.Inbetweenaremicrowaves,x-rays,infraredlight,ultravioletlight,andvisiblelight.
�141
Thereisalotoflightintheworld.Someofitisvisible.Someofitisnonvisible.Doyouthinkthatmostofthelightthathitsyoureyeislightthatyoucanseeornot?Explainyouranswer.(Thepreviouschartshouldhelpyou.)Althoughyoucannotseenonvisiblelight,yourbodycandetectitinotherways.Infraredlightmakesyoufeelwarm.Whenyougooutintothesunlight,yourskinabsorbsinfraredlight.Youcannotseethatlight,butyoucanfeelitaswarmth.Yourskinalsoabsorbsvisiblelightandultravioletlightwhenyouareinthesun.Inclass,youlearnedthattheultravioletlightfromthesuncangiveyousunburn.Eventhoughyoucannotseeit,nonvisiblelightfromthesunisveryimportantformakingEarthawarm,comfortableplacetolive.SomeWaysWeUseNonvisibleLightManyofthedevicesthatyouuseeverydayrelyonlightthatyoureyescannotdetect.Doyoueverlistentoaradio?Radiosaredesignedtodetectradiowaves.RadiowavesareatypeofnonvisiblewavegivenoffbyanantennaataradiostaCon.Justlikeyoureyedetectslightandsendsasignaltoyourbrain,aradioantennadetectsradiowavesandsendsasignaltoyourspeakers.Theradiospeakersthenproduceasoundthatyoucanhear.Radiowaveshavethelongestwavelengthofanykindoflight.Theirwavelengthcanbemanykilometerslong.Evenbeforereadingtoday,youprobablyknowsomethingaboutmicrowaves.Amicrowaveovenusesmicrowavelightwaves.Lookbackatthechartoftypesoflighttoseehowmicrowavelightcomparestoothertypes.Yearsago,scienCstsdiscoveredthatwatereasilyabsorbsmicrowavelight.Whenmicrowavesareabsorbedbywater,thetemperatureofthewaterincreases.Thisisusefultoknowbecausenearlyallofthefoodyoueathassomewaterinit.Whenyouputyourfoodinamicrowaveoven,thewaterinthatfoodabsorbsnonvisiblemicrowavelightandheatsup.Theheatedwaterthenheatsthefoodaroundit,whichmakesyourfoodhot.Lookatthisphoto.Whensomeonetakesfoodoutofthemicrowaveoven,thefoodishotbutthecontainerthefoodisinmaysCllbequitecool.WhydoyouthinkamicrowaveovencanheatfoodwithoutheaCngthebowl?Microwavesarealsousefulforsendingsignals.Hereissomethingyouprobablydidnotknow:Whenyoutalkonacellphone,yourphoneisactuallysendingandreceivingmicrowaves!UsingX-raystoSeethroughThingsWhilelongwavelengthsoflightareusefulforsendingsignalsoverlargedistances,shorterwavelengthsoflightareusefulforotherpurposes.X-raysandgammaraysmakeitpossibleforpeopletoseethroughthings.Haveyoueverbrokenabone?Ifso,adoctorprobablyusedanx-raymachinetotakeapictureofyourbones.Usinganx-raylightsource,doctorssendx-raysthroughyourbodytowardspecialphotographicfilmontheotherside.Whenx-raysstrikethefilm,theyareabsorbedandturnthefilmblack.Bonesshowupwhiteonanx-raybecausethesearetheareasofthefilmwhereveryfewx-raysareabsorbedbythefilm.Ifapersonwearsametalringwhiletheyhaveanx-ray,theringwillappearbrightwhite.Thephotoontherightshowsthis.Nowthatyouunderstandmoreaboutlight,absorpCon,andtransmission,youcanprobablyexplainthis.Doesmetalmostlytransmitorabsorbx-rays?Explainyouranswer.
�142
X-raysattheAirportX-raysareusefulforairportsecurityworkers,whocheckpassengers’luggagefordangerousmaterials.Byusingx-rays,theycanlookinsideluggagewithoutopeningit.Whenyouflyonaplane,workersshinex-raysonyourluggage.Thepicturetotherightshowswhattheysee.YoumaynoCcethattheobjectsinthispictureshowupasdifferentcolors.Anairportx-raymachineworksaliLledifferentlythanadoctor’sx-raymachine.Theobjectsdonotlooklikebones,dothey?Allx-rayshaveawavelengthofaboutasinglenanometer,buttheycanbealiLlebiggerorsmaller.Amedicalx-raymachineonlyusesonewavelengthofx-rays,butanairportmachineusesmanydifferentwavelengths.Sincedifferentmaterialsabsorbdifferentwavelengthsofx-rays,workerscantellwhatkindsofmaterialsareinsideofbags.Thishelpsthemtoknowwhethersomethingismadeofmetal,rubber,orcloth.Isthatnotamazing?Theyneverevenhavetoopenyourbagtoknowwhatisinside!However,x-rayscanbedamagingifapersonisexposedtothemtoooTen.Medicalpeoplewearmetalapronsmadeoflead,ortheystandbehindaleadwallwhentheytakex-rays.Whywouldadark-coloredclothnotworkaswellaslead?Inthisunit,youhavelearnedalotaboutlight.Youlearnedthatlightmustenteryoureyeinorderforyoutosee.Youlearnedthattherearemanywavelengthsoflightthatyoureyecannotdetect.Eventhoughyoucannotseeit,youusenonvisiblelighteveryday.Itmakesyouwarm,helpsyoucommunicate,heatsyourfood,andcanevenhelpyouseethroughthings!
�143
�144
Lesson13.3–HowwouldtheworldlookifpeoplecouldseeUVandIRlight?
Whatwasthepointofthelastlesson?
Whatwillwedo?Wewillseehowtheworldmightlookifoureyescoulddetectnonvisibleultravioletorinfraredlight.
Conclusion
1. ImagestakenwithIRandUVcamerassomeCmesappearcolorful.HowdoyouknowthatthecolorinthesepicturesmusthavebeenaddedarCficially?
2. Basedonthepicturesyouhaveseeninclass,whymightUVandIRimagerybeusefulforastronomers?
3. WhymightUVandIRimagerybeusefulforfirefighters?
4. Duringapoweroutage,thelightsinacitycanallgoout.IfyouhadachoiceofusingeitheraUVorIRcameratohelpyousee,whichonewouldyouchoose?Explainyourchoice.