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Physics > Particle Physics > Flashcards

Particle Physics Flashcards

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1
Q

Strong Nuclear Force

A

Range = 10^ -15 m (diameter of a U nucleus)
Affects = nuclear material
Purpose = binds nucleus
Relative magnitude = 1

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2
Q

Electro Magnetic Force

A

Affects = charged particles
Purpose = atomic bonding
Relative magnitude = 10^ -2

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3
Q

Weak Nuclear Force

A

Affects = all particles
Purpose = beta decay
Relative magnitude = 10^ -7

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4
Q

Gravitational Force

A

Affects = all particles
Purpose = attracts all matter
Relative magnitude = 10^ - 38

(does not affect sub atomic particles since masses are so small)

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5
Q

Ev to joules

A

ev ÷ 1.96 x 10^-19 = joules

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6
Q

joules to Ev

A

Joules x 1.96 x 10^-19 = ev

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7
Q

voltage to velocity

A

v = w/q
voltage x 1.96 x 10^-19 = energy in joules
E = 1/2 mv²
√ E ÷ 1/2 m = v

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8
Q

Momentum

A

E = 1/2 mv²

1) - for two particles to have equal 
     momentum 
   - Ek must be split inversely proportional to 
     their masses 
     (Ek ∝ 1/m)

2) - if particle at rest momentum = 0
- 2 particles will move off at equal momentums in opposite directions so net momentum = 0
- therefore ρ is conserved

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9
Q

Conservation

A

mass- energy: E = mc²

momentum: E = 1/2 mv² / (Ek ∝ 1/m)
charge: equal numbers of protons

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10
Q

Conservation in α decay

A

mass-energy: Mr U = Mr Th + Mr α + mc²
momentum: - U atom at rest
- Th and α move off in opposite
directions with equal
momentums inversely
proportional to their masses
so net ρ = 0
- α receives a larger portion of
disintegration energy
electric charge - U has 92 protons
- Th + α have 92 protons

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11
Q

Ernest Rutherford

A
  • 1st artificial transmutation (α particles)
  • N14 atoms bombarded with α radiation
  • 7N14 + 2He4 = 8O17 + 1H1
  • produced an isotope of oxygen and a
    helium atom
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12
Q

artificial transmutation

A

when one element is deliberately converted into another element

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13
Q

Cockcroft + Walton

A
  • 1st artificial transmutation using artificially accelerated particles (protons)
  • could chose how and when to initiate transmutation
  • lithium foil bombarded with protons in a linear accelerator
  • helium atoms produced with Ek
  • moved in opposite directions
  • Ek from protons conserved
  • 3Li7 + 1H1 = 2He4 + 2He4 + Ek (kinetic energy)
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14
Q

Linear accelerator

A

1) hydrogen discharge tube:
produces proton
2) proton injected into column
(evacuated tube)
3) accelerated - decreasing voltage supply
4) Li target @ 45° to the proton beam struck
5) 2 α particles produced moving 180° apart
to L + R of plate
6) detected on zinc sulfide screen - scintillation
7) microscope - flashes

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15
Q

O’Lawrence

A

cyclotron

  • particle accelerator
  • O motion: faster particles with lower voltage
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16
Q

colliding particles

A
  • Coulomb force of repulsion must be over come
  • extreme temperature + pressure
  • high velocity collisions
    = particle accelerators
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17
Q

colliding particles equation

A

p + p + Q1 = p + p + additional p + Q2

  • Q1 = energy pf incident collision
  • Q2 = energy of resultant collision
  • additional p - depends on Ek of colliding
    particles (protons)
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18
Q

Types of particle accelerators

A

linear - stanford
cyclotron - cern
combinations - Tevatron

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19
Q

cyclotron

A
  • can independently accelerate particles in two rings and introduce them to collide when they wish
  • O motion = more acceleration with less
    voltage
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20
Q

neutrino

A

proposed : Pauli
- mass-energy not conserved
- zero charge so hard to find
found : Reines and Cowan

21
Q

antimatter (positron)

A

proposed: Dirac
- eqn of E has √
- therefore + and - answer
found: Hess + Anderson (proof of positron)

22
Q

antimatter

A
  • particles with identical mass
  • opposite spin
  • takes E to create p + anti p (pair production)
  • releases E when p + anti p brought back
    together (pair annihilation)
23
Q

Pair production

A
  • the simultaneous creation of a particle and its corresponding antiparticle from electromagnetic energy
  • hf = 2(mc² ) + Ek1 + Ek2
  • photon = particle + antiparticle
24
Q

Threshold energy

A
  • minimum energy required for pair production to occur
  • if hf = threshold energy particles created at rest
  • if hf > threshold energy, extra = Ek
25
Q

conservation of momentum in pair production

A
  • particles do not move 180° apart
  • shows that gamma ray has momentum
    as p conserved and net p does not equal 0
26
Q

Pair Annihilation

A

the conversion of a particle and its corresponding anti-particle into electromagnetic energy

2(mc²) + Ek1 + Ek2 = 2hf
- particle + antiparticle = 2 photons !!!
- photons produced in pairs to conserve
momentum
- each photon of equal energy + frequency

!!greater mass = more energy!!
eg. proton annihilation > electron

27
Q

Quark

A
  • an elementary particle which experiences all four fundamental forces and forms a basic constituent of mater
  • fundamental particle
  • feels strong nuclear force
28
Q

Murray Gell-Mann

A
  • discovered quarks
  • James Joyce’s Finnegan’s wake
  • “three quarks for a muster mark”
29
Q

6 quarks/ antiquarks

A 
up
down 
top 
bottom 
strange 
charm
30
Q

Leptons

A
  • not made up of quarks
  • do not feel strong nuclear force
  • principle force = weak nuclear
  • fundamental elementary particles
    electron (-1) (e-)
    muon (-1) (μ)
    tao (-1) (τ)
    positron (+1) (e+) (anti-electron)
    (positively charged electron)
    electron neutrino (0) (Ve)
    anti electron neutrino (O)
31
Q

Hadrons

A
  • made up of quarks (not fundamental)

- feel all four forces

32
Q

Mesons

A
  • Mr between electron and proton
  • made up of 1 quark and 1 different
    antiquark
  • pion (u,D) (+1) (π+)
  • kaon (D,s) (0) (κ°)
33
Q

pion

A 
quarks = up, anti-down 
charge = +1
symbol = π+
34
Q

kaon

A 
quarks = anti-down, strange
charge = 0
symbol = κ°
35
Q

Baryons

A
  • Mr greater than or equal to a proton
  • made up of 3 quarks / 3 anti-quarks
  • proton (uud) (p+) = +1
  • neutron (udd) (n°)= 0
  • lambda (udc) (Λ+) = +1
  • sigma (dds) (Σ-) = -1
36
Q

proton

A 
quarks = up, up, down 
charge = + 1 
symbol = p+
37
Q

neutron

A 
quarks = up, down, down 
charge = 0
symbol = n°
38
Q

lambda +

A 
quarks = up, down, charm
charge = +1
symbol = Λ+
39
Q

sigma -

A 
quarks = down, down, strange
charge = -1 
symbol = Σ-
40
Q

anti-proton

A 
quarks = anti-up, anti-up, anti-down 
charge = - 1 
symbol = p -
41
Q

physical quantity the same for quark and antiquark

A

mass

magnitude of charge

42
Q

physical quantity different for quark and antiquark

A

sign of charge

spin

43
Q

beta decay (including neutrino)

A

1N1 = 1H1 + -1e0 + ve

44
Q

maximum frequency of a photon that can form an electron and a neutron by pair production

A 
hf = 2mc²
f = 2mc²/h
45
Q

why does high speed particle travel in circular motion when it enters a magnetic field?

A

force of the magnetic field is perpendicular to the velocity of the particle

46
Q

minimum frequency of photon produced by pair annihilation

A 
2mc² = 2hf
mc² = hf 
f = mc²/h
47
Q

why will the photons have more than the minimum energy?

A

in addiction to the rest mass the colliding particles will have kinetic energy

48
Q

why must particles travel at high speeds?

A

to overcome the coulomb force of repulsion

49
Q

why can two positrons not annihilate eachother

A

in conflict with conservation of charge

Physics (16 decks)

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