NUCLEAR PHYSICS RADIOACTIVITY

subtopicsofRadioactivityi NuclearPhysics2 fundamentalparticles

Theprocessof radioactivity is a randomand spontaneousprocessRandomThecountrateemittedfromanyradioactivesourcefluctuatesover time

confirmingthe randomnatureofradioactivityPlot agraphofcountrate on the yaxisagainsttime on the x axisItthegraph isnotsmooththat confirmstherandomnatureofradioactivity

count arate

graphfluctuates

mhmsame

spontaneousiThetermspontaneousnaturemeans that theprocessofradioactivitydoesnotdependon anychargestakingplace in theexternalenvironmentalconditionslie temperature pressure presence or absenceofelectriclmagneticfield ete

HowtocheckforthespontaneousnatureTaketwoidenticalradioactivesources andplace them indifferentenvironmentsie differenttemperature pressureele

Obtainthecourtrateatspecifictimeintervals from bothsourcesandplot agraphofcountrateus timeIf thevalueofhalflifeobtainedfrombothgraphs is almostthesame thenthatconfirms thespontaneousnatureoftheprocess

TYPESOFRADIATION THEIRPROPERTIES

1 AlphaparticlesDenotedby or La or HeResembles aheliumnuclei

consistsof 2 protons 2neutronsCarries a chargeof 2e where 1e e 1.6 109C ie thechargeofaprotonaparticlestravelat aspeedof 10 of thespeedoflight

e All xparticleshavethesamekineticenergy theytravelroughlythe samedistance in air ie 4 SanTheyhavelowpenetrationpowerand can bestoppedby a pieceofpaperTheyhavehighionizingeffect in ourDuring an a decay ie x emission themassnumberoftheparentnucleusdecreasesby 4 andtheprotonnumberof theparentnucleusdecreasesby2

Example X L x jobyParent DaughterNucleus Nucleus

General I L x t I 1 y

2BetaparticlesResembles an electron camDenotedby f e or gp

es achargeof Ie with a manof911 1031kgTravelwithspeedsrangingfrom 901 to99 of thespeedoflightTheyhave a rangeofkineticenergiesTheyhavemoderatepenetrationpower can passthroughpaperbut can bestoppedbyAluminumsheetsthat are a few mm thickTheyoffer a moderateionizationeffectTheydeflectinelectricandmagneticfieldsDuringBemission the man numberof the parentnucleus remains unchangedwhereastheprotonnumberincreasesby 1o Bparticles have a rangeof afewmetresin ourSince B particles are lighter than a particles theydeflectmore easilyinelectricand magneticfields

Example I X IB t I yParent DaughterNucleus Nucleus

General BA x B t BIY

whydoesprotonnumberincreaseby 1andmass number remaru constantIt isbelievedthatduringaBeurission aneutroninsidethenucleussplitstoforma protonand an electron

Theprotonstaysinsidethenucleusand theelectron is emittedfromthenucleusintheformof a Bparticle

changed

Themassnumber remains unchangedbecause a neutron islostbut aprotonisgained

Theprotonnumberchangesbecause aproton is gained

Behaviourof a and Bparticles in electricalfields

t t t t t t tstreamof a particles

s

It t t t t t

streamofBparticles 7 7multiplepathsbecauseBparticlestravelat variousspeeds

3 GammaRadiationHighfrequencyelectromagnetic radiationNeitheranymass nor anychargeDevotedby 8Travelsatthespeedoflight sinceitspartoftheEMspectrumNegligible1zero ionizationeffectMax1infiniterange in ourPassesthroughpaperandaluminum but can bestoppedby aleadsheetthata fewcm thickNodeflectioninelectric or magneticfieldsProduced inalmost all nuclearreactionsBeingEM waves theyfollow wave properties ie the intensity t ofgammaraysisinverselyproportionaltothesquareofthedistance d

I n I n

sd2 L

d2

NoteTheaboverelationship means that if wedoublethedistancefromthesourceemitting 8 rays theintensityreachingus willreducetobecome 4ofit'sinitialvalue