Physics AS Revision Notes - Excluding materials

Ive condensed a couple of text books into a small booklet! Great for revision seeing as the exams are very close

If there is anything I could improve on, or change please comment and tell me!

I AM VERY SORRY FOR ANY SPELLING MISTAKES!!!

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  • Created by: arbi_h
  • Created on: 29-04-16 19:27

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2016




PhysicsRevision
AS­REVISION(EXCLUDINGMATERIALS)
ARBI

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Waves
- Cycle=Onecompletevibrationofawave
- Displacement=Howfarapointonthewavehasmovedfromitsundisturbedposition
(metres)
- Amplitude=Maximummagnitudeofdisplacement
- Wavelength,=lengthofonewholewavecyclefromtwosimilarpoints






- Period(T),s=Timetakenforawholecycletocompleteortopassagivenpoint
- Frequency=Thenumberofcyclespersecondpassingagivenpoint
- Phase=Ameasurementofthepositionofacertainpointalongthewavecycle
- Phasedifference=Amountthatonewavelagsbehindanotheràmeasuredinangles
(degreesorradian)orasfractionsofacycle


- Reflection=Waveisbouncedwhenithitsaboundary
- Refraction=Wavechangeddirectionasitentersadifferentmediumàspeedingupor
slowingdown


- Frequencyistheinverseofperiod
#
- = f=frequency-T=period Units=1Hz=1s-1
$


- Speedofawave=wavelengthxfrequency
- = 3x108forlightinavacuum


- Longitudinalwavesvibratealongthedirectionofenergytransferàconsistsof
compressionsandrarefactionsofthemediumittravelsthrough(sound)
- TransversewavesvibrateatrightanglestothedirectionofenergytransferàallEM
wavesaretransverse

- Apolarisedwaveonlyvibratesinonedirectionàonlytransversewavesbehavelike
thissoproofthatEMaretransverse
- Polarisingfiltersonlytransmitvibrationsinonedirection

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o Polarisingglassesusesthiseffect
àblocksunwantedglareatacertain
angle






TelevisionandRadiosignalsarepolarised
- Aerialrodsarehorizontalsotheylineupwiththereceivingaerialotherwisethe
strengthofthesignalwillbelower
- Sameforradiosàaligningaerialtotransmitsandreceive



- Superposition=onethingontopoftheother
àtwoormorewavescross,theresultant
displacementequalsthevectorsumofthe
individualdisplacement



Interferencecanbeconstructiveordestructive(diagram)
- Ifcrestandtrougharen'tsamesize,thendestructiveinterferenceisn'ttotal.
- Fortheinterferencetobenoticeableàtwo(A)needtobenearlyequal

Inphasemeansinstep-twopointsinphaseinterfereconstructively
- Twopointsonawaveareinphaseiftheyarebothatthesamepointinthewavecycle
o Pointsinphasehavethesamedisplacementandvelocity(360°=2radians)

- A&B=Inphase
- A&C=Outofphase







- Twopointswithaphasedifferenceof0oramultipleof360°(fullcycle)areinphase
- Pointswithaphasedifferenceofoddnumber­multiplesof180(radians,orahalf
cycle)areexactlyoutofphase
o Twodifferentwavescanbeconsideredàhappensduetobothwavescoming
fromsameoscillatorsthereforehaveaphasedifferencebetweeneachother




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Togetinterferencepatternsthetwosourcesmustbecoherent
- Canstillhappenifthere'sadifferentwavelengthandfrequency,itsjustthatitsalla
jumbleàtwosourcesarecoherentiftheyhavethesameWAVELENGTH,FREQUENCY
andaFIXEDPHASEDIFFERENCE

- Cangetdestructive
interferencewhenthereis
ap.dofhalfawavelength,
oneandahalfwavelength
twoandahalfetc.=outof
phase




- Amountbywhichthepathtravelledbyonewaveislongerthanthepathtravelled
()*# + #
- ConstructivewhenP.D=n D.I= = +
( (

StationaryWaves:Progressivewavesreflectedataboundaryàstationary(standing)wave
isthesuperpositionoftwoprogressivewaveswiththesamefrequency(wavelength),
movinginoppositedirection
- Noenergyistransmittedbyastationarywaveàdemonstratedbysettingupadriving
oscillatoratoneandofastretchedstringwiththeotherendfixedàwavegenerated
buttheoscillatorisreflectedbackandforth
- Mostfrequencytheresultantpatternisajumbleàbutifoscillatorsproduceanexact
numberofwavesinthetimeittakesforthewavetogettotheendandback
- Atthese`resonantfrequencies'yougetastationarywavewherethepatterndoesnot
move.Itjustbobsupanddown


Stationarywavesformoscillatingloopsseparatedbynodes
- Eachparticlevibratesatrightanglestothestring.Nodeswhereamplitudeiszero
- Firstharmonic:
o


o Vibratingatlowestpossibleresonant
frequency.Ithasone"loop"withanodeat
eachend



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-

- Twicethefrequencyofthefirst
harmonic.Therearetwo"loops"withanodein
themiddleandoneateachend



-
(.
- =
)
- Whichmodeitsin




- Microwavesreflectedoffametalsurface/platesetupastationarywaveàFirstnodes
andanti-nodes
- PowdercanshowstationarywavesinatubeofairàLycopodiumpowderlaidalong
thebottomandthepowderisshakenawayfromtheantinodesbutleftundisturbedat
thenodes


Corepractical:investigatefactorsaffectingtheresonantfrequenciesofastring
1. Measuremass(M)andlength(L)ofdifferentstringtypesusingamassbalanceand
0
ruler.Thenfindthemassperunitlengthà =
.





2. Setupapparatusasshownindiagram.Recordµ,measureandrecordLandworkout
thetension(T)àT=mg màtotalmassofthemassesinkg
3. Turnonthesignalgeneratorandverythefrequencytillyoufindthefirstharmonic

- Theninvestigatehowthelength,tensionormassperunitlengthofthestringaffects
theresonantfrequency
- Showedthat:
1. Longestthestring=lowertheresonantfrequencyàhalfthewavelengthatthe
resonantfrequencyislonger
2. Theheavierthestring=lowerresonantfrequencyàwavestravelslower
makingfrequencylower
3. Looserstring=lowerresonantfrequencyàfrequencyofthefirstharmonicis
#
= (/)
(1


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Diffraction
- Amountofdiffractiondependsonthewavelengthcomparedtothesizeofthegap
o Gapgreaterthanthewavelength=diffractionunnoticeable
o Noticeablediffractionwhengapseveralwavelengthwide
o Mostdiffraction=samesizewavelength
o Gapsmaller=wavesreflectedback
- Lightshonethroughanarrowslitcanformdiffractionpatterns
o Needmonochromatic[samewavelengthandfrequency],coherentlightsource
samecolour



o
o Centralbrightfringe(centralmaximum),withdarkandbrightfringesalternating
oneitherside.Thedarkandbrightfringesarecausedbydestructiveand
constructiveinterferenceoflightwaves
- Diffractionofwhitelightcreatesaspectrum
o Centralmaxima=white
o Theblackfringesareclosertogetherandconstructivefringescreatedifferent
colours(spectra)

Intensityoflightmeansnumberofphotons
- Centralmaximaarethebrightestduetohavingthehighestintensity
6789:
- Intensity=
;:7<<<9=>?7)@1@:9@
- Formonochromaticlight,photonshavethesameenergy,soanincreaseintheintensity
meansanincreaseinthenumberofphotonspersecond
- Morephotonsperunitareahittingthecentralmaximumpersecondthantheother
brightfringes

àIncreasingslitwidthdecreasestheamountofdiffractionmeaningcentralmaximumis
narrowandtheintensityishigher
àIncreasingthewavelengthincreasestheamountofdiffractionmeaningthecentral
maximumiswider,andtheintensityofthecentralmaximumislower

Twosourceinterferenceinwaterandsounds
- Needcoherentsourcesàsamewavelengthandfrequency
- Needtousethesameoscillator…

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2. Dangerofworkingwithlasers/prevent:
o Damageretina,warningsignsoutside,wearsafetygoggles,turnofflaserwhen
notneeded

Young'sDoubleSlitformula
+B
Fringespacing- = D=distancefromslittoscreen
<
S=Slitspacing
Fringespacing­Distancefromthecentreofoneminimumtothecentreofthenext
minimumorfromonecentralmaximumtotheother

Young'sexperiment:EvidenceofwavenatureofEMradiation
- Lightcouldrefract/diffractandinterfere
- Lightmadeupoftinycorpuscles

Diffractiongradient
- CanrepeatYoung'sdoubleslitexperimentwithmorethantwoequallyspacedslits
àsamepatternbutthebrightbandsarebrighterandnarrowerandthedarkbecomes
darker
- Monochromaticlightispassedthroughagratingwithhundredsofslitspermmsothe
interferencepattersissharpàmoreaccuratemeasurement

Monochromaticlightonadiffractiongratinggivessharplines
1. Monochromaticlightàallthemaxima'saresharplines
2. There'salineofmaximumbrightnessatthecentrecalledthezeroorderline
3. Linesjusteithersideofthecentralonearecalled1storders
4. Foragratingwithslitdistancedapart,theangle
betweentheincidentbeamandthenthorder
maximum =




Derivingtheequation:
1. Ateachslit,incomingwavesarediffracted.Thesediffractedwavesinterferewith
eachothertoproduceaninterferencepattern
2. Considerthefirstmaximum,happensattheanglewhen
thewavefromoneslitline-upwiththewavesfromthe
nextslitthatareexactlyonewavelengthbehind
3. Anglebetweenfirstordermacandincominglight
4.…

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àSincan'thavegreaterthan1thereforeyou'llgettoacertainthereisnomoreorders
thatexist

DiffractionGratingshelptoidentifyelementsandcalculateatomicspacing
1. Whitelightisamixtureofcolours,ifyoudiffractwhitelightyougetaspectradueto
allthedifferentwavelengthsàspreadoutbydifferentamounts
2. Eachorder=spectrum,redontheoutsideandvioletontheinside.Thezeroorder
maximumstayswhitebecauseallpassthrough
3. Astronomersandchemistsneedtostudyspectratoidentifyelements àXrayhave
similarwavelengthtothespacingbetweenatomsincrystallinesolids àxrayforms
diffractionpatternsandthereforexraycrystallographyàstructureofDNA

RefractiveindexàMeasureofhowmuchlightslowsdown
- Lightfastestinavacuum,slowsdowninothermaterialsduetointeractingwithparticles
inthem
- Absoluterefractiveindexofamaterialn,measureofopticaldensity àRatiobetween
;
speedoflightinavacuum,c,andthespeedoflightinamaterial = àC=3x108
;K
;#
- Relativerefractiveindexbetweentomaterials,1( =
;(
)M
Combiningequationsà1n2=
)N
- Becauseweassumenair=1youcansaytherefractiveindexforairtoglass=absolute
refractiveindexofglass(orothers)

Snell'sLawusesanglestocalculatetherefractiveindex
- Angle of the incoming light makes to the normal is…

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OpticalFibresuseTotalInternalReflection
1. Step ­ index optical fibres themselves have a high ­ refractive index but are
surroundedbycladdingwithalowerrefractiveindextoallowtotalinternalreflection
+protectsfibrefromscratches(lightcouldescape)
2. Light shone in at one end of the fibres, its narrow so light always hits a boundary
betweenthefibreandcladdingatananglebiggerthanthecriticalangle àalllight
T.I.Rfromboundarytoboundary






Dispersion&Absorption:Causesignaldegradation
- Absorptioncauseslossinamplitude,someenergyisfromwhatthematerialismadeup
ofàcausinglossof(A)ofsignalbeingreduced

z





Dispersioncausespulsebroadening
- Twotypes:
1. Modaldispersion­lightraysenterfibreatdifferentanglescausingdifferentpaths.
Rayswilltakelongertotravel.Singlemodefibreonlylighttakeonepathà…

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Mechanics

- Scalaràmagnitudebutnodirection(mass,temperature,time,speed,energy)
- VectoràBothmagnitudeanddirection

- Representingvectors:
1. Lengthofthearrowrepresentsmagnitude
2. Directionofthearrowrepresentsthedirectionofthevector

Vectoraddition F1
- Vectorsalongthesamestraightline F2
- Resultant=F1+F2 Resultant

Combiningperpendicularvectors
- Tofindtheresultantoftwovectors(X,Y)actingat90°toeachotherwedrawvectorsas
adjacentsidestoeachother.Thisisduetothehorizontalandverticalcomponents
beingindependent

Y
- MagnitudeofRcanbeworkedoutbyR2=Y2+X2
T
- Directionoftheangleisworkedoutbytan =
U
X
Vectorsubtraction
- Whatistheboxesinspeed?
10m/s
o Changeinspeed=new­old
6m/s
à10­6=4ms-1

- What'sitschangeinvelocity?
o inV=newvelocity­old
o 10m/s(up)­6m/sdown
o thereforeà10­(-6)=16m/sasdownisnegative

·…

Comments

LouiseG

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ARBI my ******** computer crashed and saved the rating as 4* when I meant to press 5 b/c i was doing it on my phone and my fat fingers got in the way :(

I'm so sorry I I wanted to change it but I can't !!

Brilliant resource :D 5*

LouiseG

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Good to see you got it back up to 5* :D

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