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A-Level PHYSICS Edexcel > Topic 8 - Particle/Nuclear > Flashcards

Topic 8 - Particle/Nuclear Flashcards

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1
Q

Nucleon number

A

number of neutrons and protons in the atom

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2
Q

Proton Number

A

number of protons in the nucleus

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3
Q

Rutherford’s scattering experiment

A

A stream of alpha particles from a radioactive source were fired at a very thin gold foil sheet. The number of alpha particles at different angles was recorded

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4
Q

Rutherford’s scattering experiment conclusions

A
  • most (fast charged) alpha particles went straight through therefore an atom in mostly empty space
  • some alpha particles deflected at an angle greater than 90 therefore part of the atom must be more massive than the alpha particle this is the nucleus
  • alpha particles were repelled therefore the nucleus must be positively charged
  • since atoms are neutral overall so electrons must be in the outside of the atom
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5
Q

Nuclear model

A
  • concentrated mass in centre
  • strong positive charge in centre
  • negative charge spread across remaining atom
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6
Q

Thermionic emission

A

the process by which free electrons are emitted from the surface of a metal when external heat energy is applied

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7
Q

How do electron guns work

A
  • thermionic emmisionrelease electrons
  • electrons accelerated by electric field
  • passed through a small hole so the electrons are in a beam
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8
Q

energy gained by electron (eV) =

A

accelerating voltage

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9
Q

how does a cyclotron work

A

two semi circular electrodes with alternating charge have a gap between them. The electric field between the electrodes accelerates the charged particle across. A perpendicular magnetic field is applied to keep the particle moving in a circular path.

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10
Q

Why does the radius of a charged particle in a cyclotron increase

A

because velocity is proportional to radius so as it is accelerated the radius increases.

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11
Q

How does a LINAC work

A

A high frequency AC current is applied to the electrodes so that their charge changes from + to - . The charged particle is always repelled from the previous electrode and attracted to the next one hence causing it to be accelerated through the electric field to the next electrode.

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12
Q

Why does the length of electrodes on an LINAC increase

A

the length of the electrodes increase so that the particle has the same acceleration even when it is moving faster.
Tubes switch polarity.

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13
Q

Hadrons

A

particles that feel the strong interaction

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14
Q

Baryons

A

hadrons made of 3 quarks

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15
Q

Mesons

A

hadrons made of two quarks: a quark and an anti-quark

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16
Q

proton

A

Baryon: uud

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17
Q

Neutron

A

Baryon: udd

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18
Q

K+

A

Meson: u ŝ

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19
Q

K

A

Meson: d ŝ

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20
Q

K -

A

Meson: s û

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21
Q

π+

A

Meson: u antidown

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22
Q

π

A

Meson: u û
OR
d antidown

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23
Q

π-

A

Meson: d û

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24
Q

Anti Mesons

A

K and π are their own anti particles

Whereas K+ is the antiparticle of K-

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25
Q

Leptons

A

fundamental particles that don’t feel the strong interaction. They interact with other particles via the weak interaction, gravity and the electromagnetic force.

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26
Q

Electrons

A

stable leptons

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27
Q

Muons

A

heavy unstable leptons (eventually decays to an electron)

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28
Q

Tau

A

heaviest least stable lepton

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29
Q

Neutrino

A

Electrons, Muons and Taus have their own neutrino which has zero mass and zero charge

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30
Q

Neutron decay

A

unstable so decays to a proton via beta decay

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31
Q

Antiparticles

A

each particle has a corresponding antiparticle with identical mass and opposite charge, baryon and lepton numbers

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32
Q

E=mc^2

A

energy can turn into mass and mass can turn into energy.

when energy is converted to mass you make equal amounts of matter and antimatter

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33
Q

pair production

A

if a particle is produced an anti-particle must also be produced

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34
Q

Relativity

A

the mass of an object increases as velocity increases due to relativistic effect

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35
Q

converting from kg to MeV/c^2

A
  • convert mass to energy (e=mc^2)

- convert to MeV

36
Q

converting from MeV/c^2 to kg

A
  • Convert to J/C^2

- divide by C^2

37
Q

eV -> joules

A
  • e
38
Q

joules -> eV

A

/ e

39
Q

production of an anti particle pair

A

only happens if gamma proton has enough energy to create mass. happens near a nucleus to conserve momentum.

40
Q

Annilihation

A

occurs when a particle meets an anti-particle. All mass is converted into energy

41
Q

Conservation Laws in Particle Reactions

A
  • charge
  • Baryon Number
  • Lepton Number
  • Mass/energy
  • momentum
42
Q

detecting charged particles

A

charged particles cause ionisation therefore leave a trail of ions

43
Q

Cloud chambers

A

supercooled vapour condenses when a particle passes through

44
Q

Bubble chambers

A

Hydrogen kept as a liquid (above normal boiling point). If you quickly reduce the pressure bubbles of gas form where there are trails of ions

45
Q

Charged particles in magnetic field

A

circular paths

46
Q

Charged particles in electric fields

A

parabolic paths

47
Q

spiral paths

A

the particle is interacting and losing energy

48
Q

Neutral particle tracks

A

there aren’t any

49
Q

Why are collisions high energy

A

Energy required to overcome electrostatic repulsion. Since particles move fast the energy/momentum must be high, shorter de broglie wavelength.

50
Q

Why are linac tubes at the end the same length?

A

the speed of the particle has become a maximum

51
Q

ionisation

A

Electrons have been removed/added from a molecule

52
Q

charged particle in magnetic field

A

circular

53
Q

charged particle in electric field

A

parabolic (tries to get in line with electric field)

54
Q

Why don’t photons leave a trail

A

they’re neutral

55
Q

When two particles are formed from a photon why do their tracks curve away from each other?

A

they are in a magnetic field implying one is positively charged and one is negatively charged, charge is conserved.

56
Q

what does the curvature of the spirals for a charged particle in a magnetic field tell you?

A

the momentum of the particle (more momentum means bigger radius)

57
Q

difference between electric field and magnetic field on a charged particle

A

electric might do work but magnetic field never does work

58
Q

When alpha particles are fired at a gold foil what happens to most of them/ what does this mean?

A
  • they pass straight through

- most of the atom is empty space

59
Q

Why are some alpha particles scattered through 180 when fired at gold foil?

A
  • most of the mass is in the centre which is charged positively hence deflecting the positive charge of the alpha particle
60
Q

what is the force that causes deflection of charged particles?

A

electrostatic repulsion

61
Q

What happens to the path of deflection if the charge is twice as much?

A
  • deflection starts earlier

- the final deflection is greater

62
Q

Use of electric fields in particle detectors

A
  • used to accelerate/deflect particles

- direction of deflection indicates charge (work is done to make particle move in same direction as the field)

63
Q

derive a = EQ/m

A 
F = EQ F=ma
a = EQ/m
64
Q

use of magnetic fields in particle detectors

A
  • produces circular motion
  • direction of curvature indicates force (flemings LHR)
  • momentum found from radius of curvature
65
Q

Kinetic energy transferred when a charge accelerates across a potential difference

A

E = QV

66
Q

why are only a low proportion of decays detected?

A
  • emmisions in all directions
  • some emitted particles may be absorbed by the material in the sample
  • some emitted particles may be absorbed by the window
  • some pass through the detector
67
Q

creation

A

creates a particle and an antiparticle. E = mc^2

68
Q

annilhation

A

a particle and its anti-particle are destroyed simultaneously in a conversion to energy (2 photons)

69
Q

electronvolt

A

energy required to accelerate an electron through a pd of 1v

70
Q

Antimatter

A

same mass, opposite charge (+other properties)

71
Q

electric fields…

A

accelerate particles (speed up + change direction)

72
Q

magnetic fields…

A

accelerate particles (change the direction into a circular path)

73
Q

what can particle tracks be used to work out?

A
  • charge
  • mass
  • energy
74
Q

LINAC

A

a series of electrode tubes of increasing length with an AC pd applied across them

75
Q

what does firing electrons at a hydrogen target tell us

A
  • proton is not uniform, it has some empty space since some electrons passed through
  • made up of smaller particles called quarks
76
Q

fundamental particle

A

has no internal structure / not made up of other particles

77
Q

atomic process that produces emission spectra

A

electron drops down energy levels and de-excites releasing energy

78
Q

why were scientists able to predict the 6th quark?

A
  • standard model symmetry
  • quarks came in pairs
  • 6 known leptons by only 5 known quarks
79
Q

why is GeV/c a unit of momentum

A

GeV/c^2 is a unit of mass

p = mv

80
Q

Why did it take a long time to find experimental evidence for the top quark

A

large mass, needs a lot of energy

81
Q

quark order

A

Up, Down, Charm, Strange, Top, Bottom

82
Q

Last quark to be discovered

A

Top

83
Q

lightest quark

A

up

84
Q

heaviest quark

A

top

85
Q

lambda particle

A

baryon: u d s

A-Level PHYSICS Edexcel (16 decks)

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