Physics of the atom. radiaoctive decay..ppt

Physics of the atom. radiaoctive decay.

1. DetectionofRadioactivity
CharacteristicsoftheThreeTypesofEmissionNuclear
Reactions
Half-Life
UsesofRadioactiveIsotopesIncludingSafety
Precautions

2. Describethedetectionofalpha-particles,beta-particlesandgamma-rays
byappropriatemethods.

3. Radioactivityistheprocesswhereby
unstableatomicnucleireleaseenergetic
subatomicparticles.
Radioactivitywasfirstdiscoveredin1896by
theFrenchscientistHenriBecquerel,after
whichtheSIunitforradiation,the
Becquerel,isnamed.
Radioactivity 3

5. Radiationcannotbedetectedwithourfive
senses,specialdetectorsaretherefore
needed.
Severaldeviceshavebeendevelopedto
detectradioactivity,withtheearliestbeingan
unexposedphotographicplateplacedinthe
vicinityofasourcebeingdetected.
Otherdevicesinclude:
thecloudchamber,
electroscopes,
theGeiger-Müllertube
Radioactivity 5

6. ItwasnamedforHansGeigerwhoinventedthedevicein1908andWalther
MüllerwhocollaboratedwithGeigerindevelopingfurtherin1928
Radioactivity 6

7. Radioactivity 7

8. Cloud chamber

12. • When radiation passes through a gas,
some of the gas molecules may lose
electrons and this causes ions to be
formed. The gas is considered ionized.
• In descending order of ionizing power:
α, β and γ
Ionizing Power

13. Theproductsofradioactivitycouldbe
analyzedintothreedistinctspeciesby
eitheramagneticfieldoranelectricfield.
15

15. Radioactive decay

18. Half-life
The half-life of a radioactive substance is
thetime takenforhalf of the nucleiin a
sample to undego radioactive decay.

23. Half-life calculations

26. Aradioactiveelementhasahalf-lifeof40
minutes.Theinitialcountratewas1000per
minute.Howlongwillittakeforthecountrate
todropto250perminute?
Half-life = 40 min
1000----500----250 (3 half-lives)
3 x 40 min = 120 min

27. Nuclear Fission

30. Nuclear Fusion

32. Wecannotdomuchtoreduceourexposure
tonaturalbackgroundradiation,butgreat
careisneededwhenhandlingradioactive
materials.Precautionsinclude:
Radioactivity 72

33. wearingprotectiveclothing
Radioactivity 73

34. keepingasfarawayasispracticable-
forexample,byusingtongsorrobotic
arms.
Radioactivity 74

35. keepingradioactivematerialsinlead-
linedcontainers,labelledwiththe
appropriatehazardsymbol.
Radioactivity 75

36. keepingyourexposuretimeasshort
aspossible
Radioactivity 76

37. Discussthewayinwhichthetypeofradiationemittedandthehalf-life
determinetheuseforthematerial.

38. Aradioactiveisotopeisintroducedintoaliving
system,whereitflowsalongthebloodstream,
followingthepathofchemicalprocesses
therein.
ItiseasilydetectedusingascannerorGeiger
counter.Thescannertakepicturesandarerun
togetherinrapidsuccession,givingphysicians
amovie-likeviewoftheisotope'spath.
Whentheprocedureisfinishedtheisotopeis
flushedoutofthebodyalongwithother
wasteproducts.
Radioactivity 78

40. Acommonprocedureistheinjectionof
iodine-131fortheobservationofthethyroid
gland.Ahealthythyroidwillaccumulateanyiodine
enteringthebody.
Whenaphysicianscansthepatient,ifiodine-
131ispresentinthethyroid,theglandis
workingproperly.
However,ifthetraceelementhasnotcollected
inthethyroid,thephysicianknowstheglandis
failing.
Radioactivity 80

41. Radioactivity 81

42. Amethodfordeterminingthepositionofa
leakinaconduitorpipeline.
Short-livedradioisotopeisinsertedintothe
conduitorpipelineandiscausedtomove
alongitbypressuringuptheconduitor
pipelinefromoneorbothendsthereofwith
fluid,forexamplewater.
Thecarrierbodytravelstotheleakbutno
furtheranditslocationisdetectedfrom
outsidetheconduitorpipelineusinga
radiationdetector.
Radioactivity 82

43. Radioactivity 83

44. Asourceofbetaradiationisusedtopassbeta
particlesthroughthepaper.
Adetectorontheothersideofthepaperdetects
thebetaparticlesthatpassthrough.
Thedetectorisconnectedtoahydrauliccontrolvia
a
processorunit.
Iftheradiationleveldetecteddropsitmeansthe
paperistoothicksothehydrauliccontrolpushes
rollersclosertogetherinordertoreducethepaper
thickness.
Iftheradiationleveldetectedincreasesitmeans
thepaperistoothinsothehydrauliccontrolpulls
therollersapartsothepaperthicknesscanbe
increased.
Radioactivity 84

45. Radioactivity 85

46. RadiocarbondatingusestheamountofCarbon14
(C14)availableinlivingcreaturesasameasuring
stick.
Alllivingthingsmaintainacontentofcarbon14in
equilibriumwiththatavailableintheatmosphere,
rightuptothemomentofdeath.Whenanorganism
dies,theamountofC14availablewithinitbeginsto
decayatahalfliferateof5700years
ComparingtheamountofC14inadeadorganismto
availablelevelsintheatmosphere,producesan
estimateofwhenthatorganismdied.
88
https://www.youtube.com/watch?v=L8Eyyh2Vpfs&t=609s

47. Carbon-14hasahalf-lifeof5700years.
1.Cro-Magnonmanisoneofourancestors.Fiveadult
skeletonswerefoundnearLesEyziesinFrance.A1g
sampleofcharcoalfromthissiteproduceda
radioactivecountof0.5countsperminute.Amodern
sampleofcharcoalofsamemassproducesacountrate
of32countsperminute.Bothcountswerecorrected
forbackgroundradiation.HowlongagodidCro-
Magnonmanlive?
2.A10-gsampleofwoodcutrecentlyfromalivingtree
has anactivityof160counts/minute.Apieceof
charcoaltakenfromaprehistoriccampsitesalsoweighs
10gbuthasanactivityof40counts/minute.Estimate
theageofthecharcoal.
Radioactivity 89

48. 3.Awoodenpostfromanarchaeologicaldig
produces150countsperminute.Woodfroman
identicalspeciesoftreecurrentlyalivegives600
countsperminute.Howlongagodidthewood
fromthearchaeologicaldigdie?
4.Inacarbon-datingexperimentasampleofwood
fromanobjectwasburntandthecarbondioxide
producedwascollected.Theactivityofthecarbon
dioxidewasequivalentto2.25countperminute
pergramofcarbon.Whenthesameexperiment
wasrepeatedusingwoodfromamodernsource,
thecorrectedcountswas18countperminuteper
gramofcarbon.Whatisthelikelyageofthefind?