Midterm 3 Flashcards
Whichofthefollowingstatementsbestdescribesthequantumpropertyspin?
A)Spinisameasureoftherotationrateofasubatomicparticle
B)Spinisnotmeanttobetakenliterallybutmeasurestheinherentangularmomentumofasubatomicparticle.
C)Spinisapropertythatappliesonlytolargeobjects,likebaseballs.
D)Spinisameasureoftherateatwhichaparticlespinsaround(orbits)anotherparticle.
E)Spinisnotafundamentalpropertybutrathersomethingthatcanchangerandomlyatanytime.
Spinisnotmeanttobetakenliterallybutmeasurestheinherentangularmomentumofasubatomicparticle.
Anupquark(u)hasacharge+2/3,andadownquark(d)hasachargeof—1/3.Whichofthefollowingdescribesaproton?
uud
Thetwofamiliesof
fundamentalparticlesoutof
whichallordinarymattersmadeare
leptonsandquarks.
Thefourfundamentalforcesare
strongforce,weakforce,electromagneticforce,gravity
Supposethat,throughthemalicious actofaneight-dimensionalalienbeing, thestrongforcewassuddenlyturned offthroughouttheuniverse.Whatwould happenalmostimmediatelytoatoms?
Thenucleiofatomswouldfallapart.
Accordingtotheuncertaintyprinciple,
whichofthefollowingstatementsistrue?
Itisimpossibletomeasureboththeposition
andthevelocity ofaparticleatthe
sametime.
Whichofthefollowingstatementsbest describestheexclusionprinciple? A)Ifaparticlehasapreciselydefinedposition, itisexcludedfromhavingapreciselydefined momentum. B)Twophotonscannotbeinthesameplace atthesametime. C)Thelawsofquantummechanicsare excludedfromapplyingtolargeobjects madeofmanyatoms. D)Thelawsofquantummechanicsare excludedfromourcommonsense. E)Twofermionscannotoccupythesame quantumstateatthesametime.
Twofermionscannotoccupythesame
quantumstateatthesametime.
Whichofthefollowingwillcause thedegeneracypressurewithinanobject toincrease? A)compressingittohigherdensity B)loweringitstemperature C)lettingitexpandtolowerdensity D)raisingitstemperature E)shiningalightonit,whichaddsradiative energy
compressingittohigherdensity
Whichofthefollowingstatementsabout
quantumtunnelingistrue?
A)Itisusedinmodernelectronics,and,
infact,ourmodern daycomputers
wouldnotworkwithoutit.
B)Itplaysacrucialroleinnuclearfusion
intheSun.
C)Itallowselectronsandothersubatomic
particlestopassthroughwall-likeenergy
barriersevenwhenitseemstheydo
nothaveenoughenergytogetthroughthebarriers.
D)Althoughithasbeenobservedtooccur,
itviolatesallotherknownlawsofnature,
andexplainingittherefore
representsamajorchallengetophysicists.
E)A,B,andCaretrue,butDisnot
E)A,B,andCaretrue,butDisnot
Whichofthefollowingbestexplains
thephenomenonofblackholeevaporation?
A)Blackholeevaporationisavirtualprocess,
meaningthatithasbeentheorizedbyastrophysicistsbutdoesn’treally
occur.
B)Particles(orantiparticles)arecreatedby
aquantummechanicaleffectnear,butoutside,
theeventhorizonoftheblack
hole.Thelawofconservationofenergymaintains
thattheblackholemustloseenergyto”pay”forthecreationofthis
mass.
C)Virtualparticlescreatedneartheblack
holeareconstantlyannihilatingeachother,causinga
veryhightemperature
eveniftheblackholehasnoaccretiondisk.
Thishightemperatureprovidesescapevelocityforthe
virtualparticles,causingtheentire”cloud”ofvirtualparticles
toexpandawayintospace.
D)Duetohightemperaturesintheaccretiondiskarounda
blackhole,materialevaporatesfromtheblackholelikewater
evaporatingfromtheocean.
E)Particles(orantiparticles)areoccasionallyejectedfrom
withintheeventhorizon,causingtheblackholetolosemass.
Particles(orantiparticles)arecreatedbya
quantummechanicaleffectnear,
butoutside,theeventhorizonofthe
blackhole.Thelawofconservationofenergy
maintainsthattheblackholemustloseenergyto
“pay”forthecreationofthis
mass.
Whichofthefollowingstatementsabout
degeneracypressureisnottrue?
A)Degeneracypressurestopsthegravitational
collapseofordinary(mainsequence)starsliketheSun.
B)Degeneracypressurearisesonlywith
fermions(suchaselectrons,protons,andneutrons)
andnotwithbosons(suchasphotonsorheliumnuclei).
C)Degeneracypressurestopsthegravitational
collapseofwhitedwarfs.
D)Explainingtheoriginofdegeneracy
pressurerequiresboththequantummechanicalexclusionprincipleandthe
uncertaintyprinciple.
E)Degeneracypressurehaltsthecollapse
ofneutronstars.
Degeneracypressurestopsthe
gravitationalcollapseofordinary(mainsequence)starsliketheSun.
Inthelate1800s,KelvinandHelmholtz
suggestedthattheSunstayedhot
thankstogravitationalcontraction.
Whatwasthemajordrawbackofthisidea?
ItpredictedthattheSuncouldlast
onlyabout25millionyears,whichis
farlessthantheageofEarth.
Whatdowemeanwhenwesaythat
theSunisingravitationalequilibrium?
ThereisabalancewithintheSun
between theoutwardpushofpressure
andtheinwardpullofgravity.
WhatistheSunmadeof?
70percenthydrogen,28percenthelium,
2percentotherelements
ThephaseofmatterintheSunis
plasma.
Fromthecenteroutward,whichofthe
followingliststhe”layers”oftheSun
inthecorrectorder?
core,radiationzone,convectionzone,
photosphere,chromosphere,corona
Sunspotsarecoolerthanthe
surroundingsolarsurfacebecause
strongmagneticfieldsslow
convectionandpreventhotplasma
fromenteringtheregion.
Thefirststepintheprotonprotonchainproducesanantielectron,orpositron.
Whathappenstothepositron?
Itisrapidlyconvertedtoenergywhen
itmeetsanordinaryelectron,resulting
inmatterantimatterannihilation.
Theoverallfusionreactionbywhich
theSuncurrentlyproducesenergyis
4H 1He+energy.
Supposethat,forsomeunknownreason,
thecoreoftheSunsuddenlybecamehotter.
Whichofthefollowingbest
describeswhatwouldhappen?
A)Thehighertemperaturewouldnotaffect
thefusionratebutwouldcausethecoretoexpand
andcooluntilthetemperaturereturnedtonormal,
withthecoreatanew,slightlylargersize.
B)Highertemperaturewouldcausetherateof
nuclearfusiontorise,whichwouldincreasethe
internalpressure,causingthecoretoexpandand
turntheSunintoagiantstar.
C)Highertemperaturewouldcausetherateof
fusiontofall,decreasingtheinternalpressure
andcausingthecoreto
collapseuntiltherateoffusionreturnedtonormal.
D)Highertemperaturewouldcausetherateof
nuclearfusiontorise,whichwouldincreasethe
internalpressure,causing thecoretoexpandandcooluntilthe
fusionratereturnedtonormal.
Highertemperaturewouldcausetherateof
nuclearfusiontorise,whichwouldincrease
theinternalpressure,causing thecoretoexpandandcooluntilthe fusionratereturnedtonormal.
Whathappenstoenergyintheconvectionzoneof
theSun?
Energyistransportedoutwardbytherising
ofhotplasmaandthesinkingofcoolerplasma.
Whatprocessesareinvolvedinthesunspot
cycle?
thewindingofmagneticfieldlinesdueto
differentialrotation
Sinceallstarsbegintheirliveswiththesame
basiccomposition,whatcharacteristicmost
determineshowtheywilldiffer?
masstheyareformedwith
Astar’sluminosityisthe
totalamountoflightthatthestarwill
radiateoveritsentirelifetime.
Ifthedistancebetweenusandastaris
doubled,witheverythingelseremainingthe
same,theluminosity
remainsthesame,buttheapparent
brightnessisdecreasedbyafactoroffour.
Supposethatyoumeasuretheparallax
angleforaparticularstartobe0.5arcsecod.
Thedistancetothisstaris
2parsecs.
Whichofthefollowingstatementsaboutspectral
typesofstarsistrue?
A)AstarwithspectraltypeAiscoolerthana
starwithspectraltypeB.
B)Thespectraltypeofastarcanbeusedto
determineitssurfacetemperature.
C)Thespectraltypeofastarcanbeusedto
determineitscolor.
D)AstarwithspectraltypeF2ishotterthana
starwithspectraltypeF3.
E)Alloftheabovearetrue.
Alloftheabovearetrue.
Supposeyouseetwomain-sequencestars
ofthesamespectraltype.Star1isdimmerin
apparentbrightnessthanStar2byafactorof100.
Whatcanyouconclude?(Neglectanyeffectsthatmight
becausedbyinterstellardustandgas.)
Star1is10timesmoredistantthanStar2.
Whichofthefollowingtermsisgiventoapairofstarsthatwecandetermineareorbitingeachotheronlyby
measuringtheirperiodicDopplershifts?
A)doublestar
B)spectroscopicbinary
C)visualbinary
D)eclipsingbinary
E)noneoftheabove
spectroscopicbinary
OnaHertzsprung-Russelldiagram,wherewouldwefind
starsthathavethelargestradii?
upperright
Youobserveastarinthediskofthe
MilkyWay,andyouwanttoplotthestaron
anH-Rdiagram.Youwillneedto
determineallofthefollowing,exceptthe
rotationrateofthestar
Whichofthefollowingistrueaboutlowmassstarscomparedtohighmassstars? A)Low massstarsarehotterandmore luminousthanhighmassstars. B)Low massstarsarecoolerandless luminousthanhighmassstars. C)Low massstarsarecoolerbutmore luminousthanhighmassstars. D)Low massstarshavethesametemperature andluminosityashighmassstars. E)Low massstarsarehotterbutless luminousthanhighmassstars.
Lowmassstarsarecoolerand
lessluminousthanhighmassstars.
WhyareCepheidvariablessoimportant
formeasuringdistancesinastronomy?
Theirluminositycanbe
inferredfromtheirperiod.
Clusteragescanbedeterminedfrom
mainsequenceturnoff.
Thetypicaldensityandtemperatureof
molecularcloudsare
300moleculespercubic
centimeter,1030Kelvin.
Ifyouwantedtoobservestarsbehind
amolecularcloud,inwhatwavelength
oflightwouldyoumostlikely
observe?
infrared
Thethermalpressureofagasdepends
on
densityandtemperature.
Whatpreventsthepressurefrom
increasingasacloudcontracts
duetoitsgravity?
Excesspressureisreleasedin
jetsofmaterialfromtheyoungstars.
Whatisthelikelyreasonthat
wecannotfindanyexamples
ofthefirstgenerationstars?
Thefirstgenerationstarswere
allverymassiveandexplodedassupernova.
Whendoesastar
becomeamainsequencestar?
whentherateofhydrogenfusionwithinthestar’scoreis
highenoughtomaintaingravitationalequilibrium
Whichofthefollowingdiscoveries,
iftheyexisted,wouldnecessitate
areevaluationofourideasofstellar
formation?
a0.01
solarmassstar
Whatpreventsabrowndwarf
fromundergoingnuclearfusion?
Degeneracypressurehaltsthecontraction
ofaprotostarsothecoreneverbecomes
hotordenseenoughfornuclearfusion.
