topic 7: atomic, nuclear and particle physics

7/24/2019 Topic 7: Atomic, Nuclear and Particle Physics

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Topic 7: Atomic, nuclear and particlephysics

7.1 – Discrete energy and radioactivity

Discrete energy and discrete energy levels The electrons of an atom can occupy certain discrete atomic energy levels.

As an electron makes a jump from one energy level to another, energy is

absorbed or released in the form of a photon. The amount of energy absorbedor released is equal to the difference beteen the discrete atomic energy levelsand is also quanti!ed.

The energy of a photon is dependent on its frequency. Therefore, only photonsith frequencies hich correspond to the differences beteen the atomic energylevels can be absorbed or released by an atom. These frequencies appear asspectral lines in the emission and absorption spectra.

http:""astro.unl.edu"naap"hydrogen"graphics"bohr#transitions.png

The e$istence of discrete energy levels called atomic energy levels can be

supported by the emission spectra and the absorption spectra of atoms.

http:"".bu!!le.com"images"diagrams"hydrogen%spectrum.jpg

Transitions beteen energy levels&hen the electrons ithin an atom jump from one atomic energy level to a loer

energy level, energy is released in the form of light. 'ikeise, light is absorbed henthe electrons ithin an atom jump from one atomic energy level to a higher energy



level.

https:""upload.ikimedia.org"ikipedia"commons"f"f("Absorption#or#emission#spectr oscopy.png

https:""classconnection.s).ama!onas.com"*7)"flashcards"+*77*7)"jpg"+-)*## gh%+-+7A+*/01-2-()7(/.jpgThe amount of energy absorbed or released can be calculated by the difference in

energy 3e45 beteen the to energy levels.

6adioactive decay 6adioactive decay refers to the spontaneous random process by hich particles

or electromagnetic radiation is emitted from an unstable nucleus. The productnucleus from a radioactive decay is called a daughter nucleus.

The daughter nucleus is energetically unstable.

The activity of radioactive decay can be shon e$ponentially or by half%lives.

http:""-.bp.blogspot.com"%*q7gqb$s8"9t;*!c8n<"AAAAAAAA&;o"=4b9e>%?ge<"s+2")%(%decayrates./.png



htp:"").bp.blogspot.com"%o9@@h(mp"9taBkoDf?<"AAAAAAAA&aC"9h1aAf<u7g"s+2")%(%decayrates.++.png

The decay constant represents the probability of decay of a nucleus per unit

time and is dependent on the type of radioactive particles.

http:"".saintlouisradon.com"cmss#files"imagelibrary"half(life(diagram.jpg

The radioactive half%life of a substance is the time it takes for half of its

radioactive nuclei to decay. <f e plot the amount of radioactive nuclei hich have not yet decayed ith time,

the resulting curve is called the decay curve and can be shon as the folloing.

http:"".kgs.ku.edu"C$tension"gifs"halflife.gif

1undamental forces and their properties



http:""hyperphysics.phy%astr.gsu.edu"hbase"forces"imgfor"funfor+.gif

http:""hyperphysics.phy%astr.gsu.edu"hbase"forces"imgfor"funfor(.gif

http:""hyperphysics.phy%astr.gsu.edu"hbase"forces"imgfor"funfor).gif

http:""hyperphysics.phy%astr.gsu.edu"hbase"forces"imgfor"funfor-.gif

Alpha particles, beta particles and gamma raysAlpha particles

http:""+.bp.blogspot.com"%%c190@%g6"9$l+AElqF<"AAAAAAAA&b"7yGu7ds/C"s+2")%(%decaymodes.++.gif An alpha particle is a helium nucleus.

<t has a relative charge of H(.

<ts penetration poer is the loest among the three types of particles and can

be blocked by a piece of paper or a fe cm of air. <ts ioni!ing poer is the highest among the three types of particles.

Beta particles



http:""+.bp.blogspot.com"%d4't6I!u0gk"9$@m6-gy<"AAAAAAAA&g<"#0%na$m*2"s+2")%(%decaymodes.+)d.gif

http:""-.bp.blogspot.com"%j%EucA#h*"9$mFj6g!-<"AAAAAAAA&c9"?Dl8f?%1A*"s+2")%(%decaymodes.+.gif A beta particle is an electron or a positron.

<t has a relative charge of %+ or H+.

<ts penetration poer is in the middle among the three types of particles and can

be blocked by a thin sheet of aluminum. <ts ioni!ing poer is in the middle among the three types of particles.

Gamma rays

http:""+.bp.blogspot.com"%l<pnFdkp4@8"9$m9l=!Eo<"AAAAAAAA&cs"7co*7otq1c"s+2")%(%decaymodes.+7.gif ?amma rays are photons.

<t does not have a charge.

<ts penetration poer is the highest among the three types of particles and can

be blocked by several cm of lead. <ts ioni!ing poer is in the loest among the three types of particles.



http:""hyperphysics.phy%astr.gsu.edu"hbase"nuclear"imgnuc"radpen.gif

http:""hyperphysics.phy%astr.gsu.edu"hbase"nuclear"imgnuc"alpbet.gif

>alf%lifeGee previous section 36adioactive decay5.

Absorption characteristics of decay particlesGhort%term effects 'ong%term effects

6adiation burn

Fausea and vomiting

Diarrhea

>eadache

ancer

?enetic mutations

<sotopes

http:""(.bp.blogspot.com"%;?F->l<Gk"9$laiETj&<"AAAAAAAA&bB"n4a0t'c"s+2")%(%decaymodes.2.gif Different isotopes of a given element have the same atomic number 3atomic numberdefines the type of element5 but different mass numbers because they have differentnumbers of neutrons.

0ackground radiation0ackground radiation comes from natural sources and artificial sources. Fatural sources: cosmic rays from space, radioactive rocks and soil, living

organisms that have consumed radioactive substances in the food chain Artificial sources: radioactive aste from nuclear poer plants, radioactive



fallout from nuclear eapons, medical $%rays

Average composition and e$posure of background radiation

http:"".bbc.co.uk"staticarchive"(/7db7-)d/bf-f-bef7de*ebf(*+2d)cb.gif

https:""upload.ikimedia.org"ikipedia"commons"("("6adiation#Dose#hart#by#kcd.png

7.2 – Nuclear reactions

The unified atomic mass unit

The unified atomic mass unit 3J5 is commonly used in nuclear physics. <t is definedas one telfth of the mass of a carbon%+( atom.

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Bass defect and nuclear binding energyMass defect The difference beteen the mass of an atom and the sum of mass of its

constituent parts is called its mass defect. Bass defect can be e$plained by CinsteinMs mass%energy equivalence: As

energy required to break apart a nucleus, the sum of energy contained in theconstituent nucleons is higher than that of the combined nucleus. Cnergy isrelated to mass.

Nuclear inding energy The nuclear binding energy of a nucleus is the amount of ork required to

separate the nucleons inside the nucleus. 0inding energy per nucleon L binding energy of nucleus " number of nucleons in

nucleus.

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7(*.jpgKcbL+)(27)/7)here C is energy in E, m is mass in kg, and c is the speed of light in m"s

1<The nuclear binding energy curve

http:""hyperphysics.phy%astr.gsu.edu"hbase"nucene"imgnuk"bcurv.gif

Fuclear fission and nuclear fusionNuclear fission Fuclear fission is the splitting of a heavy nucleus into to lighter nuclei.

A great amount of energy is released in nuclear fission due to the greater

binding energy of the daughter nuclei. Fuclear fission is used in nuclear poer plants.



Nuclear fusion Fuclear fusion is the joining of to light nuclei to form a heavy nucleus.

A great amount of energy is released in nuclear fusion due to the greater

binding energy of the daughter nucleus.

Fuclear fusion yields more energy than nuclear fission. Fuclear fusion is the main source of the sunMs energy.

http:""u(.lege.net"cetinbal"AC"AtomicbombA(.jpg

7.! – "he structure of matter

8uarks, leptons and their antiparticles 8uarks and leptons are the elementary particles 3building blocks5 of matter.

Cach particle also has an antimatter counterpart.

&hen matter collides ith its corresponding antimatter, the particles annihilate

and release energy by mass%energy equivalence.

http:""crescentok.com"staff"jaske"isr"ps"quark(.jpg

>adrons, baryons and mesons



http:""physicsnet.co.uk"p%content"uploads"(+""IArticle%classification.gif As stated in the previous section, the elementary particles of matter comprises

of quarks and leptons. >adrons are made up of quarks and are identified in the same classification

level as leptons. 9nlike leptons, hich do not e$perience the strong nuclear force, hadrons

e$perience all four fundamental forces. >adrons are generally larger than leptons.

>adrons are sub%divided into baryons and mesons.

0aryons and mesons are made up of different types of quarks and antiquarks.

http:""ffden%(.phys.uaf.edu"(++#fall((.eb.dir"0rian#armak"baryon#antibaryon.jpg

http:""ffden%(.phys.uaf.edu"(++#fall((.eb.dir"0rian#armak"mesons.jpghere u represents up quarks, d represents don quarks, c represents charm

quarks, s represents strange quarks, 3t represents top quarks5, b represents bottomquarks, and the line above the representative letter of the quarks indicate itscorresponding antiquarks.

The conservation las of charge, baryon number,

lepton number and strangeness &hen riting equations, e already kno that the charge of the reactants and

the products must be identical due to the conservation la of charge. <n particle physics, other than the conservation of charge, the baryon number,

lepton number, and strangeness must also be conserved. 0aryons have a baryon number of H+, antibaryons have a baryon number of %+,

leptons have a lepton number of H+, and antileptons have a lepton number of %+. The conservation of strangeness 3strange quark5 only occurs ithin interactions



of the strong nuclear force hile the conservation of the other three propertiesapply to all interactions.

The nature and range of the strong nuclear force, eak

nuclear force and electromagnetic forceGee previous section in 7.( 31undamental forces and their properties5.

C$change particlesC$change particles of the four fundamental forces are gluons, photons, &H bosons,&% bosons, ; bosons, and gravitons.

http:""cronodon.com"images"8D#2.jpgGee previous section in 7.( 31undamental forces and their properties5.

1eynman diagrams 1eynman diagrams, introduced by physicist 6ichard 1eynman, can be used to

e$press the behavior of subatomic particles over time. 1eynman diagrams are read from the left to the right here the $%a$is shos

time and the y%a$is shos roughly the space direction of the subatomic particleinteractions. Gome 1eynman diagrams, such as the e$amples given belo,sitch the $%a$is and the y%a$is here the progression of the interactions ithtime is read upards.

http:""scienceorld.olfram.com"physics"fimg**.gif

Gome e$amples of 1eynman diagrams



http:""hyperphysics.phy%astr.gsu.edu"hbase"particles"imgpar"feynm.gif

http:""hyperphysics.phy%astr.gsu.edu"hbase"particles"imgpar"feynm).gif

1or a comprehensive guide on ho to dra 1eynman diagrams, visithttp:"".quantumdiaries.org"(+"("+-"lets%dra%feynman%diagams".

onfinement8uarks and gluons 3massless subatomic particles that transmit the force bindingquarks together in a hadron5 are color%charged particles. Gimilar to electrically%charged particles hich interact by e$changing photons in electromagneticinteractions, color%charged particles e$change gluons in strong force interactions.Fote that color charge has nothing to do ith visible colors. <t is just an e$pression.

&hen to quarks are close to each other, they e$change gluons and create a strongcolor force field that binds quarks together. The force field gets stronger as thequarks get further apart. 8uarks constantly change their color charges as theye$change gluons ith other quarks. There are ) color charges and ) correspondinganti%color charges.

http:""ed.fnal.gov"projects"labyrinth"games"lanorder"particle#families"graphics"mesons#co#e$plain(.gif

Eust as mi$ing red, blue, and green visible colors yield hite, mi$ing red, blue, andgreen color charges yield color neutral.

olor confinement is a phenomenon that color%charged particles cannot be isolatedsingularly and therefore cannot be directly observed. The color%charged quarks aresaid to be confined in groups 3hadrons5 ith other quarks hich composite to colorneutral and cannot be distinguished separately. This is because the color forceincreases as the color%charged quarks are pulled apart.

T'ND6: olor confinement or quark confinement is the phenomenon hen isolatedquarks and gluons cannot be observed.

The >iggs boson<n addition to the three generations of leptons and quarks 3see previous section38uarks, leptons and their antiparticles55, there are four classes of bosons and anadditional highly massive boson called the >iggs boson. This particle as proposedin +/2- to e$plain the process hich particles can acquire mass and as identifiedith the 'arge >adron ollider 3'>5.



http:""atlas.ch"nes"images"stories"bosons%image.jpg

1<The 'arge >adron ollider 3'>5 is the orldMs largest and most poerful particlecollider, the largest and most comple$ e$perimental facility ever built, and the largestsingle machine in the orld. <t as built by C6F in collaboration ith over +scientists and engineers from over + countries along ith hundreds of universitiesand laboratories.

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@ur changing vies of the atom model

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Gummary of fundamental particles and interactions



http:"".quick%facts.co.uk"images"medium#particle#chart.jpg

topic 7: atomic, nuclear and particle physics

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