atomic physics – part 3 ongoing theory development to accompany pearson physics powerpoint...

Atomic Physics – Part 3Atomic Physics – Part 3Ongoing Theory DevelopmentOngoing Theory Development

To accompany To accompany Pearson PhysicsPearson Physics

PowerPoint presentation by R. [email protected]

17.1 Detecting and Measuring Subatomic 17.1 Detecting and Measuring Subatomic ParticlesParticles

ToolsTools

Cloud Chamber: supersaturated vapour Cloud Chamber: supersaturated vapour condenses along track of particlecondenses along track of particle

Bubble Chamber: Liquid gas near its boiling Bubble Chamber: Liquid gas near its boiling point boils along track of particlepoint boils along track of particle

Recall analysis of alpha, beta, and gamma Recall analysis of alpha, beta, and gamma for charge and relative massfor charge and relative mass


More tools:More tools:

Particle accelerators: use high energy Particle accelerators: use high energy particles to probe matterparticles to probe matter

High energy “probe particles” required to High energy “probe particles” required to overcome the strong nuclear forceovercome the strong nuclear force

TypesTypes: cyclotron, linear accelerator, : cyclotron, linear accelerator, synchotron, Van de Graaff, CERN’s LHCsynchotron, Van de Graaff, CERN’s LHC


Check and ReflectCheck and Reflect, page 835, question 5, page 835, question 5

Note: particle notation uses lines on top for Note: particle notation uses lines on top for antiparticles, e.g. antiparticles, e.g. nn = neutron, = = neutron, = antineutronantineutron

n

17.2 Quantum Theory and the Discovery of 17.2 Quantum Theory and the Discovery of New ParticlesNew Particles

AntimatterAntimatter

Positrons postulated by Dirac, verified by Positrons postulated by Dirac, verified by AndersonAnderson

Matter/anti-matter collision annihilationMatter/anti-matter collision annihilation

ee++ + e + e-- 2 2 γγ Why Why mustmust there be 2 there be 2 gamma photons?gamma photons?


At this point in time, theory has predicted At this point in time, theory has predicted and evidence has supported existence of and evidence has supported existence of over 300 subatomic particles over 300 subatomic particles

Subatomic masses are communicated for Subatomic masses are communicated for convenience in units of convenience in units of

Einstein’s equation can be Einstein’s equation can be rewritten as rewritten as

2eV

c2E mc

2

Em

c


eV eV and and MeVMeV are units of energy, therefore are units of energy, therefore

are units of mass are units of mass

1 = 1.7827 x 101 = 1.7827 x 10-36-36 kg kg (you don’t need to know (you don’t need to know

this!)this!)

Your formula sheet records masses of all Your formula sheet records masses of all first generation “fermions” this wayfirst generation “fermions” this way

2 2 and MeVeVc c

2eV

c

17.4 Quarks and the Standard Model17.4 Quarks and the Standard Model

Moving to the Standard Model:Moving to the Standard Model:

Read Read Pearson PhysicsPearson Physics pages 836-8 and pages 836-8 and 842-3842-3

Read SNAP pages 366-9Read SNAP pages 366-9


Standard ModelStandard Model: (1963 originally with many : (1963 originally with many updates)updates)Fermions (make up matter)

Bosons (mediating particles)

quarks

leptons

udsc bt

(+ anti ofeach)

1st gen

make up hadrons

eμτνe

νμ

ντ

(+ anti ofeach)

baryons(3 quarks)

mesons (2 quarks)1 reg, 1 anti

includingproton uudneutron udd


Further: Further: hadronshadrons interact by the strong interact by the strong nuclear force (e.g. protons and neutrons)nuclear force (e.g. protons and neutrons)

LeptonsLeptons do not (e.g. electrons) do not (e.g. electrons)

BosonsBosons are virtual particles that mediate are virtual particles that mediate forcesforces

WW++, , WW--, , ZZ mediate weak nuclear force mediate weak nuclear force

photonsphotons mediate electromagnetic force mediate electromagnetic force

gluonsgluons mediate strong nuclear force mediate strong nuclear forcegravitonsgravitons mediate gravitational force mediate gravitational force unconfirmedunconfirmed

existence confirmed


Formula sheet chart:Formula sheet chart:

Keep this chart in front of you for the next section


Beta decayBeta decay

You already learned that in You already learned that in beta negativebeta negative decay, a neutron becomes a protondecay, a neutron becomes a proton

How can we understand this in terms of How can we understand this in terms of quarks and mediating particles?quarks and mediating particles?


neutron neutron → → proton + beta negative + antineutrinoproton + beta negative + antineutrino

udd udd →→ uud + uud + ee-- + +

(hadron) (hadron) (lepton) (lepton)

23

e13

e

13

e 23

e23

e

13

e

charge = 0 charge = +1e

to make this occur, a d quark has turned into a u quark by the following process:

d → u + [W-]

[W-] → e- + boson mediating weak nuclear force

very short lifetime


proton proton → → neutron + beta positive + neutrinoneutron + beta positive + neutrino

uud uud →→ udd + udd + ee++ + + νν

(hadron) (hadron) (lepton) (lepton)

23

e13

e

13

e23

e23

e

13

e

charge = 0charge = +1e

to make this occur, a u quark has turned into a d quark by the following process:

u → d + [W+]

[W+] → e- + ννboson mediating weak nuclear force

very short lifetime

Beta positive decay:


Standard Model Summary:Standard Model Summary:

•• All matter composed of 12 fundamental All matter composed of 12 fundamental particles and their antiparticles ……..particles and their antiparticles ……..

•• electromagnetic force and weak nuclear electromagnetic force and weak nuclear force are different aspects of the same force are different aspects of the same forceforce

•• electromagnetic and nuclear forces electromagnetic and nuclear forces mediated by virtual particles called mediated by virtual particles called bosonsbosons

We are done!!!We are done!!!

atomic physics – part 3 ongoing theory development to accompany pearson physics powerpoint...

Documents