phya1 particles and quantum phenomena - no exam questions

8/19/2019 PHYA1 Particles and Quantum Phenomena - No Exam Questions

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AS1 Particles, Quantum Phenomena and Electricity

AS-1-1 What is Physics?Objectives:

• Understand what science is

• Understand what physics is

• Explain the “scientific method”

• A very rief overview of all of physics

What is Science?!ael the followin" with S #science$, % #not science$, & #not sure$

Physics

Acupuncture

Astronomy

'me"a ( increases )Q

Astrolo"y

*hemistry

+omeopathy

Evolution

eo"raphy

*reation Science

-iolo"y

En"ineerin"

)ntelli"ent .esi"n

/odern /edicine

+istory

//% vaccines cause autism

0heolo"y

En"lish

hat separates science from non2sciences #the cartoons mi"ht help$3

1


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ExperimentsScience is ased on the experiments4

14 Scientists ma5e oservations64 *ome up with a hypothesis or theory

(4 /a5e a prediction74 *arry out an experiment to confirm or refute a theory84 'ther scientists attempt to repeat the experiment to validate it

A theory can never e proved, ut if we "et enou"h evidence we "o with thetheory until somethin" unexplained comes alon"4

ive ( reasons why scientists do experiments3

0o confirm a theory, to refute a theory, to validate #or invalidate$ anotherscientists experiment

hat does it mean to validate an experiment3

%epeated y another scientist to chec5 reliaility and repeataility and thatthey didn9t ma5e a mista5e

+ypothesis is one prediction #can include an explanation or not$

0heory is wider in scope #doesn9t :ust explain one thin"$ and must include anexplanation of why somethin" is happenin"4

/ar5 each of these as hypothesis #+$ or theory #0$

14 )f you let "o of an o:ect it will fall #+$64 Planets move in elliptical orits #+$(4 All o:ects are attracted to other o:ects dependin" on mass and

distance etween them #0$

hen scientists "et conflictin" evidence• *hec5 the experiments for mista5es in method

• %epeat to chec5 for mista5es when carryin" it out

• *ome up with a new theory or hypothesis that explains oth results4

6


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Which Science is this?

!ael the followin" with P ; Physics, * ; *hemistry, - ; -iolo"y, ' ; other4

“Everythin"” is made of atoms

Atoms contain electrons

0he &ucleus contains protons and neutrons

&eutrons and Protons are made of


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AS-1-2 The AtomObjectives:

• .escrie an atom and it9s components

• Understand mass and atomic numers

• .o specific mass calculations

Specification(4141 *onstituents of the atomProton, neutron, electron. Their charge and mass in SI units andrelative units. Specifc charge o nuclei and o ions. Atomic mass unitis not required.Proton number Z, nucleon number A, nuclide notation, isotopes

istory of Atoms All thou"h it was proposed far earlier and used as a useful idea in *hemistry

Einstein proved that atoms #or molecules$ were real in 1>?8 with his paper on-rownian motion4)n 1@> the electron was discovered and if atoms existed an electron was partof it4)n 1>?> %utherford at /anchester University explained ei"er and /arsden9sexperiment of firin" alpha particles at "old foil, as provin" the existence of thenucleus4)n 1>1@ %utherford also discovered the nucleus contained protons4)n 1>(6 Bames *hadwic5 proved the existence of the neutron4

!"mbers

&ucleon ; a particle found in the nucleus, a proton or neutron4Elements can e written li5e this

X A Z A ; /ass &umer C numer of nucleons C numer of protons D numer ofneutrons ; Atomic &umer C numer of protons C numer of electrons in a neutralatomF ; *hemical symol&umer of neutrons C A ;

e4"4 caron 17 is written as C 14

6 , it has protons and 17 ; C @ neutrons4

)sotopes are atoms which contain the same numer of protons #and aretherefore the same element$ ut different numers of neutrons4

7


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*omplete the tale#sotope e$ement n"mber

ofn"c$eons

n"mberofprotons

n"mber ofne"trons

C 14

6 *aron 17 @

Ra226

88 %adium 66 @@ 1(@

Tl 209

81 0hallium 6?> @1 16@

U 23592 Uranium 6(8 >6 17(

%ass an& 'har(eu ; atomic mass unit

Electron*har"e #e$ C 214? G 1?21> *

%est /ass #me$ C >411 G 1?2(1 5" C 848 G 1?27 u

Proton*har"e #2e$ C 14? G 1?21> *%est /ass #mp$ C 14H#($ G 1?

26H 5" C 14??H6@ u

&eutron*har"e C ?%est /ass #mn$ C 14H#8$ G 1?

26H 5" C 14??@H u

Specific 'har(e ) char(e to mass ratio ) char(e * mass

1$ *alculate the specific char"e of the proton, neutron and electron4

Electron C 214H G 1?11 *5" 21

Proton C >48@ G 1?H *5" 21

&eutron C ? *5"21

6$ *alculate the specific char"es

a$ C 14

6

7411 G 1?H *5" 21

$ U 235

92

(4H8 G 1?H *5"21

8


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AS-1-+ ,i(htObjectives:

• .escrie the photon model of li"ht

• .escrie and explain the photoelectric effect

• *alculate wor5 functions

Specification(4141 Particles, antiparticles and photonsPhoton model o electromagnetic radiation, the Planck constant,E = hf = hc!3.1.2 The photoelectric e"ect#ork unction $, threshold requenc% o, photoelectric equation h &$ ' (k) the stopping potential e*periment is not required.

What is $i(ht?

)n the late 1Hth

century there was i" deate amon" scientists aout whetherli"ht was a wave or particle4

As of the 1Hth *entury

Evi&ence for $i(ht as ave Evi&ence for $i(ht as partic$e

%efraction )t didn9t diffract

%eflection

A wave of what3

&ewton favoured the particle model of li"ht and won the day for the most partthrou"h sheer force of reputation4

0he wave theory of li"ht "ains popularity when it was shown li"ht couldproduce interference patterns4

)n the 1@7?s Iaraday showed that li"ht could e polari=ed and su""ested itwas wave of electroma"netism4

0his was confirmed in 1@H( y /axwell when he pulished the mathematical

description of li"ht waves4

)n 1>?8 Einstein entered the fray with his explanation of the photoelectriceffect, which won him the &oel pri=e4


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Photoe$ectric effect.raw a dia"ram of the photoelectric effect4

Sometimes when li"ht is shone on some metals electrons are "iven off,causin" a small current4

hat are some of the variales in this experiment3

hat factor#s$ would you expect to chan"e whether electrons are "iven off ornot3

hat factor#s$ would you expect to chan"e the current3

hat factor#s$ would you expect to chan"e the numer of electrons "iven off3

hat factor#s$ would you expect to chan"e the speed of the electrons "ivenoff3

.o the experiment

hat factor#s$ chan"es whether electrons are "iven off or not3

hat factor#s$ chan"es the current3

hat factor#s$ chan"es the numer of electrons "iven off3

hat factor#s$ chan"es the speed of the electrons "iven off3

H


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• hether electrons are "iven off or not depends only on the colour of

li"ht #fre


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0he electron volt4)onisation and excitationK understandin" of ioni=ation and excitation in thefluorescent tue4

Ener"y levels and photon emission

!ine spectra #e4"4 of atomic hydro"en$ as evidence of transitions etweendiscrete ener"y levels in atoms4hf C E1 ; E6

E$ectron T"be A particle accelerator uses an electric field to accelerate particles to hi"hspeeds4 An electron accelerated throu"h 1L "ains 1 electron volt #eL$ in ener"y4Usin" the e


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Ener"y levels in a hydro"en atom

A free electron is defined to have an ener"y level of ?40herefore all the ener"y levels are ne"ative

An electron can "et excited y "ainin" ener"y and movin" up one or moreener"y levels4

)t can only do this y asorin" one photon4

)f the photon ener"y does not precisely match the ener"y difference etweentwo levels then the photon cannot e asored4

An electron can loose ener"y y movin" down ener"y levels if it emits onephoton with the ener"y difference etween the two levels4

21 E E hf −=

hat is the fre


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ac to the $ine spectra0he "as lamp wor5s y

• electrons in the "as are accelerated y a hi"h volta"e

• these electrons collide with electrons in atoms excitin" them

• the electrons then fall ac5 down as they loose ener"y y emittin" a

photon

• these photons have discrete fre


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AS-1-4 What is an E$ectron?

Objectives:

• .escrie the evidence for the wave nature of particles

• *alculate the momentum of a particle

• *alculate the de -ro"lie wavelen"ths of particles

Specification(4146 ave Particle .uality*andidates should 5now that electron diffraction su""ests the wave nature ofparticlesK details of particle diffraction are not expected4

.e -ro"lie wavelen"thmv

h=λ , where mv is the momentum4

istory

)n 1>67 .e -ro"lie proposed the wave nature of electrons to extend -hor9smodel of the atom eyond hydro"en4

)n 1>6H it was experimentally confirmed that electrons were not only "uidedy waves ut were waves when electron diffraction was oserved4

%oment"m/omentum is defined as mass times velocity and is measured in 5"ms214

mv p =

14 *alculate the momentum of these particles

a$ Electron travellin" at 1 G 1?H ms21

>411 G 1?267 5"ms21

$ Proton travellin" at 1 G 1?H ms21

14H G 1?26? 5"ms21

c$ &eutron travellin" at 648 1 G 1?H ms21

741> G 1?26? 5"ms21

d$ Electron travellin" at @47 cmh21 in a metal

641( G 1?2(8 5"ms21

.e ro($ie Wave$en(th

16


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0he wavelen"th of a particle is related to its momentum4 So the wavelen"th of an electron depends on it9s ener"y and therefore speed4

mv

h=λ

0his applies to all o:ects ut the wavelen"th is too small to e experimentallyconfirmed for macroscopic o:ects li5e people4

64 hat is the wavelen"th of

a$ Electron travellin" at 1 G 1?H ms21

H46@ G 1?211 m

$ Proton travellin" at 1 G 1?H ms21

(4>H G 1?217 m

c$ &eutron travellin" at 648 1 G 1?H ms21

148@ G 1?217 m

d$ Electron travellin" at @47 cmh21 in a metal

(141 m

Wave Partic$e ."a$itySometimes the electron ehaves li5e a wave, sometimes in ehaves li5e aparticle4 0his is called wave2particle duality4 0his applies to all particles4

1(


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AS-1-5 Antimatter

Objectives:

• Mnow what an antiparticle is

• Mnow the properties includin" mass, char"e and rest ener"y of anti2

particles when "iven the particle e


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Each particle has an antiparticle which is identical except that the char"e andthe (@468H 14? G 1?21>

Antiproton 14H( G 1?26H >(@468H 214? G 1?21>

&eutron 14H8 G 1?26H >(>4881 ?

Antineutron 14H8 G 1?26H >(>4881 ?

Electron >411 G 1?2(1 ?481?>>> 214? G 1?21>

Positron >411 G 1?2(1 ?481?>>> 14? G 1?21>

0he antiparticle of the photon is the photon4

hat is the difference etween a neutron and the antineutron3

Annihi$ationhen a particle meets its antiparticle they annihilate, convertin" their massand 5inetic ener"y into pure ener"y4

0his ener"y ecomes a pair of photons, each with half the total ener"y4

0he rest ener"y of a particle is the ener"y produced when the particleannihilates from rest4

Pair Pro&"ction

18


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A photon of sufficient ener"y can chan"e into a particle and it9s antiparticle4

0he photon9s ener"y needs to e "reater than twice the rest ener"y of theparticle4

0he excess ener"y ecomes the 5inetic ener"y of the particles4

1


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AS-1- 8a&iation an& the case of the missin( ener(y

Objectives:

• Mnow the e


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A$pha &ecay'ne example of alpha decay is Uranium 6(@4

α 4

2

234

90

238

92 +→ ThU

)n alpha decay the nucleus looses 6 neutrons and 6 protons4

eta &ecay0horium 6(7 then under"oes eta decay4

β 01

234

91

234

90 −+→ PaTh

Examp$es*omplete the followin" nuclear e6 ; 6 C >?

loo5 this up in theperiodic tale

6(7 ; ? C 6(7

>? ; #21$ C >? D 1 C >1

loo5 this up in theperiodic tale


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%issin( Ener(y an& %oment"m)n eta decay a neutron turns into a proton and an electron4

e pn 01

1

1

1

0 −+→

+owever, if you add up all the rest ener"ies and 5inetic ener"ies the neutron

has a little it more ener"y than the proton and the electron4

Also the momentum doesn9t add up either4

0here must e another undetected particle that has the missin" ener"y andmomentum4

0his is called a neutrino #)talian for little neutral particle$ or technically forreasons we9ll discover soon, an antineutrino4

0he symol for the neutrino is ν, the ree5 letter nu4

0hus, the full e


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AS1-< Partic$e =oo

Objectives:

• Mnow all the re


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,eptons

! a m e

S

y m b o $

% a s s 6 2 ( 7

8 e s

t E n e r ( y

6 % e 9 7

' h

a r ( e 6 e 7

,

e p t o n

1

a r y o n

S t r a

n ( e n e s s

Electron −e >411G1?2(1 ?4811 21 1 ? ?

Positron +e >411G1?2(1 ?4811 1 21 ? ?

Electron&eutrino

eν 2 W ?4?????66X ? 1 ? ?

Antielectronneutrino

eν 2 W ?4?????66X ? 21 ? ?

/uon − µ 14@@G1?26@ 1?84H 21 1 ? ?

Antimuon + µ 14@@G1?26@ 1?84H 1 21 ? ?

/uon&eutrino

µ ν 2 W ?41HX ? 1 ? ?

Antimuon&eutrino µ ν 2 W ?41HX ? 21 ? ?

0auParticleX

−τ (41HG1?26H 1HHH 21 1 ? ?

AntitauParticleX

+τ (41HG1?26H 1HHH 1 21 ? ?

0au&eutrinoX

τ ν 2 W 1848 ? 1 ? ?

Antitau&eutrinoX

τ ν 2 W 1848 ? 21 ? ?

X Mnowled"e of this is not re


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%esons

! a m e

S

y m b o $

% a s s 6 2 ( 7

8 e s

t E n e r ( y

6 % e 9 7

' h

a r ( e 6 e 7

,

e p t o n

1

a r y o n

S t r a

n ( e n e s s

&e"ativePion

−π 647>G1?26@ 139.6 21 ? ? ?

PostivePion

+π 647>G1?26@ 139.6 1 ? ? ?

&eutralPion

0π 6471G1?26@ 135 ? ? ? ?

&e"ative5aon− K @4@?G1?26@ 7>(4H 21 ? ? 21

Positive5aon

+

K @4@?G1?26@ 7>(4H 1 ? ? 1

&eutral5aon

0 K @4@HG1?26@ 7>H4H ? ? ? 1

Antineutral5aon

0 K @4@HG1?

26@ 7>H4H ? ? ? 21

0he neutral pion is it9s own antiparticle4

aryons

! a m e

S y m b o $

% a s s 6 2 ( 7

8 e s t E n e r ( y

6 % e 9 7

' h a r ( e 6 e 7

, e p t o n

1 a r y o n

S t r a n ( e n e s s

Proton p 14H(G1?26H 938.3 1 ? 1 ?

Antiproton p 14H(G1? 26H 938.3 21 ? 21 ?

&eutron n 14H8G1?26H 939.6 ? ? 1 ?

Antineutron n 14H8G1? 26H 939.6 ? ? 21 ?

-aryons have aryon numer 1 Antiaryons have aryon numer ;1&on aryons have aryon numer ?

66


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'onservation ,as Are these possile3

Example 1+−

++→+ π ν µ µ

p p

- C 1 D 21 C ?! C ? D ? C ?S C ? D ? C ?Q C 1 D 21 C ?

- C ? D ? D? C ?! C 1 D 21 D ? C ?S C ? D ? D ? C ?Q C 21 D ? D 1 C ?

So this possile4

Example 6

µ ν µ ++→

+

n p

- C 1! C ?

S C ?Q C 1

- C ? D 1 D ? C 1! C 21 D ? D 21 C 26

S C ? D ? D ? C ?Q C 1 D ? D ? C 1

So this is not possile, lepton numer conservation is ro5en4

en ν π π +→+ −+

een p K K ν +++→+ −00

µ ν π π µ ++→+

− 00 p

−

+→+ e pn eν

6(


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Extra ,epton 8"$e!eptons are always alanced with the same neutrino4 So if an electron isinvolved it will e an electron neutrino4

Stran(eness

*onservation of stran"eness may e violated under some circumstanceswhich we9ll loo5 at in 6 topics time4

.ecay All ut the li"htest of each class is unstale, meanin" it will decay4

/uons and 0au particles #and their antiparticles$ decay into electrons #orpositrons$4

All aryons decay into protons4

0he only stale aryon is the proton4

A free neutron has a half life of 11 minutes4

eta .ecay 8evisite&So the revised eta decay e


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AS-1-> Three "ars for %"ster %ar

Objectives:

• Mnow the char"e and


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"ar Properties

!

a m e

S y

m b o $

8 e s t E n e r ( y

6 % e 9 7

' h a

r ( e 6 e 7

1 a

r y o n

S t r a n

( e n e s s

Up u 148 ; (4(3

2+

3

1?

Antiup u 148 ; (4(3

2−

3

1− ?

.own d (48 ; 4?3

1−

3

1?

Antidown d (48 ; 4?3

1+

3

1− ?

*harmX c 11? ; 1(7? 3

2+

3

1?

AnticharmX c 11? ; 1(7?3

2−

3

1− ?

Stran"e s H? ; 1(?3

1−

3

121

Antistran"e s H? ; 1(?3

1+

3

1− 1

0opX t 1>,1?? ; 1H(,(??3

2+

3

1?

AntitopX t

1>,1?? ; 1H(,(?? 32

−3

1−

?

-ottomX b 71(? ; 7(H?3

1−

3

1?

AntiottomX b 71(? ; 7(H?3

1+

3

1− ?

&ot re


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Partic$e "ars Partic$e "ars

+π d u −π d u

0π uu or d d

+ K su − K su

0 K sd 0 K sd

hy is the 0π it9s own antiparticle3

S"mmary0hus we have three "enerations of 6 Quar5s and 6 !eptons and theirantiparticles4

@eneration # ## ###

"ars

u c t

d s b

,eptons

e µ τ

eν µ ν τ ν

As far as we 5now this is it, except where does the photon fit3 'M, so there9sa few others, ut only 8 #or maye ut we haven9t found the +i""s -oson$,ut we9ll "et to that next lesson4

eta &ecay yet a(ainB)n eta decay a neutron decays into a proton4 So uud udd → , so a d decaysinto a u4

eeud ν ++→ −

[ou need to 5now oth the aryon and the


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AS1-1C 3orces

Objectives:

• .escrie the stron" nuclear force

• Mnow the fundamental forces

• Explain the concept of exchan"e particles

• /atch exchan"e particles and forces

Specification(4141 Stale and unstale nuclei0he stron" nuclear forceK its role in 5eepin" the nucleus staleKshort2ran"e attraction to aout ( fm, very2short ran"e repulsion elow aout?48 fmKParticle interactions*oncept of exchan"e particles to explain forces etween elementary particles

0he electroma"netic forceK virtual photons as the exchan"e particle40he wea5 interaction limited O 2, OD decay, electron capture and electron2protoncollisionsK D and 2 as the exchan"e particles4+adrons are su:ect to the stron" nuclear force4!eptons are su:ect to the wea5 interaction4

Stron( !"c$ear 3orce A nucleus contains positive protons and neutral neutrons4 0he laws ofelectrodynamics would su""est the nucleus should fly apart4 0he fact that itdoesn9t su""ests there is an attractive force holdin" the nucleus to"ether4

0his is called the stron" nuclear force #in AS Physics and more commonly thenuclear force$4 )t has a very short ran"e around ( fm4 -elow 648 fm it isstron"er than the electrostatic repulsion etween 6 protons4

+owever, in neutron stars #o:ects the mass of stars ut consistin" entirely ofneutrons$, there are no protons4 So why doesn9t the neutron star collapse intoa lac5 hole30he nuclear force is repulsive elow around ?48 fm, 5eepin" the neutronsapart4

S"mmary

• very short ran"e force #W( fm$

• ?48 ; ( fm attractive

• W ?48 fm repulsive

3orces!ist all the forces you can thin5 of

6@


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3"n&amenta$ 3orces0here are actually only 7 forces4 All other forces are :ust examples of these 740hey are called the fundamental forces4

0hey are electroma"netic, "ravity, stron" and wea54

All the forces we feel and encounter #except "ravity$ are caused y theelectroma"netic force of the electrons in atoms4

0he stron" nuclear force etween nucleons is the left over or residual stron"force actin" on the nucleon9s


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o forces or+ow can forces act at a distance3hat carries the force etween 6 particles that are not touchin"3

Iorces wor5 y exchan"in" virtual particles which carry ener"y and

momentum4

“Lirtual” ecause the particles cannot e detected or intercepted since thiswould stop them carryin" the force4

Exchan"e particles are called "au"e osons

3orce Exchan(e Partic$es

Stron" 2 "luon

Electroma"netic γ 2 photon

ea5 +! , −! , 0 "

ravity ravitonX

X not experimentally confirmed yet

S"mmary of Partic$e Exchan(e

• Particle A emits a "au"e oson

#"au"e oson is created$

• 0he "au"e oson carries ener"y and momentum

• Particle - asors the "au"e oson

#"au"e oson is destroyed$

(?


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Partic$e S"mmary0ale of all particles in existence #as far as we 5now$

Q u a r 5 s

u c t

, a u " e - o s o n s

γ

d s b

! e p t o n s

e µ τ ±!

eν µ ν τ ν

0 "

"raviton

#Plus the antiparticles$4

0he standard model also proposes that there is one more particle, the +i""9s-oson which is responsile for "ivin" the other particles mass4 )t has not yet#as of 6??>$ een discovered4

Assumin" no )/Ps N

(1


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AS1-11 Ooh Pretty Pict"res

Objectives:

• Mnow the re


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3eynman .ia(ram &issecte&

0he an"le on a feynman dia"ram si"nifies asolutely nothin"4

((

t i m e

Arrows show whether the particle is"oin" in or comin" out

#reactant or productin *hemistry spea5$

avy line to show"au"e oson

*onservation of Q,!,- apply

n → −+ ! pQ ? 1 ; 1 C ?! ? ? D ? C ?- 1 1 D ? C 1

*onservation of Q,!,- apply

−! → ee ν +

−

Q 21 21 ; ? C 21! ? 1 D 21 C ?- ? ? D ? C ?

au"e oson line is movin" up soparticle is emitted y neutron

#left side is lower so it is earlier$


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eta P$"s .ecay.raw the feynman dia"ram for eta plus #positron$ decay

een p ν ++→ +

E$ectron capt"reSometimes a proton in a nucleus can “"ra” or “capture” an electron from theinner electron shell4

ene p ν +→+ −

.raw the feynman dia"ram4#+intJ 0he electron is in the lowest ener"y level so it won9t have the ener"y tocreate a "au"e oson4$

E$ectron Proton 'o$$ision An hi"h ener"y electron collides with a proton ma5in" a neutron and an

electron neutrino4

(7


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ene p ν +→+ −

.raw the feynman dia"ram#+intJ 0his time the electron has the extra ener"y to ma5e the "au"e oson4$

!e"tron !e"trino 'o$$isionrite the e


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+

+→+

en p eν

The i( Six[ou need to memorise these dia"rams and e


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AS1-12 S"mmary

Objectives:

• Summarise and %eview Unit

• Physics unanswered $

Quar5 compositions of aryons and mesons

Existence of antimatter

7 forces and their "au"e osons

Ieynman dia"rams

aveYparticle duality for electrons and photons #photoelectric effect, electrondiffraction$

0he atom # X A

Z $

Electrons #ener"y levels and line spectra$&ucleus Protons and neutrons Quar5s

(H


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Physics Dnansere& "estions

.oes the +i""9s -oson exist3

+ow does Quantum ravity wor53

.oes the "raviton exist3

hy is "ravity so wea53

Are

phya1 particles and quantum phenomena - no exam questions

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