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A-level AQA Physics > Chapter 1: Particle Physics > Flashcards

Chapter 1: Particle Physics Flashcards

1
Q

What are the three forces acting on the nucleons in the nucleus?

A
  1. electrostatic repulsion of +ve protons
  2. strong nuclear force- attractive force that holds the nucleus together
  3. gravitational force-causes all nucleons to attract to each other due to their masses (but its a lot weaker than electrostatic forces)
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2
Q

What is the strong nuclear force?

A

a force that acts on all nucleons that is attractive up to a range of 3fm and repulsive below a range of about (0.5fm), it is responsible for the stability of a nucleus
(overcomes the electrostatic repulsion of protons)

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3
Q

What is the shape of a graph to represent strong nuclear force?

A

-maximum attractive force is at 1fm
-force becomes 0 at 3fm
-until 0.5fm, repulsion is never zero because no two masses can ever be in the exact same place in the universe
(should be able to draw graph and with a comparison for electrostatic force!!!!!!!!!!!)

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4
Q

What is the range for the strong nuclear forces?

A

attractive - up to 3fm

repulsion - below 0.5fm

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5
Q

What is nuclear decay?

A

when unstable nuclei emit particles to become more stable

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6
Q

From what type of particles are alpha particles decayed from?

A

large nuclei because they are too big for the strong nuclear force to keep them stable
too many protons/neutrons/both

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7
Q

What is alpha decay and what is its formula?

A

-helium nucleus (2 protons and 2 neutrons)

ᴬzX——- ᴬ-⁴z-₂X + ⁴₂α

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8
Q

In what type of particles does beta decay occur?

A

nuclei with too many neutrons

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9
Q

What is beta-minus decay?

A

emission of an electron with an antineutrino
a neutron turns into a proton and an electron is emitted
antineutrino particle carries away some energy and momentum

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10
Q

What is the formula for beta-minus decay?

A

ᵃzX——–> ᵃz+₁W + ⁰₁β + ̅νe

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11
Q

What is beta plus decay?

A

a proton turns into a neutron and a positron and an electron neutrino are released

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12
Q

What is frequency?

A

the number of complete waves that pass a point per second

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13
Q

What is wavelength?

A

the distance between two adjacent crests of a wave

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14
Q

What is the EM spectrum

longest wavelength—shortest wavelength

A 
radio waves
micro-waves
infrared
visible light
ultraviolet
X-rays
gamma rays
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15
Q

What is a photon?

A

a packet of EM radiation that has a specific (discrete) amount of energy, it transfers energy and has no mass

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16
Q

What is the formula for the speed of light?

A

c = f * λ

c=3x10⁸

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17
Q

What is the formula for photon energy? (two versions)

A

E= h * f or E= h*c/λ

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18
Q

What is h?

A

planck’s constant

6.63x10⁻³⁴

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19
Q

What can a beam of photons be related to?

A

a beam of photons can be related to generating a POWER

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20
Q

What is the formula for power (in terms of photons)

A

P=nhf
n=number of photons per second
P=power-W

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21
Q

What is an electron volt?

A

an eV is the energy required to increase an electron’s energy through one volt (V=E/Q)
energy in joules = charge of an e⁻ x 1V

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22
Q

What is 1 eV and 1 Mev in Joules?

A

1 eV=1.6x10⁻¹⁹J

1 MeV= 1.6x10⁻¹³J

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23
Q

What is antimatter and three properties?

A

a particle that has opposite properties to its corresponding matter

  • same rest mass and rest energy
  • has opposite charge
  • will destroy its counterpart
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24
Q

What is annihilation?

A

when a particle meets its corresponding antiparticle, ALL of the matter is converted to two gamma ray PHOTONS that move in opposite directions to conserve momentum (draw the diagram)

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25
Q

Describe the way photons travel after annihilation?

A

they move in opposite directions and perpendicular to matter/antimatter to conserve momentum

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26
Q

What is pair production?

A

when energy is converted into mass, then you get equal amounts of matter and antimatter
it always produces a particle and its corresponding antiparticle

27
Q

What condition is required for pair production to occur?

A

it only happens if there is enough energy to produce the masses of the particles

28
Q

What is the minimum energy required for pair production?

A

the total rest energies of the particles that are produced
Eₘᵢₙ=2E₀
E₀ is the rest energy of particle type produced

29
Q

What is usually produced from pair production?

A

electron-positron pairs
because they have relatively low mass
low mass means low rest energy so less energy is required for the pair production to happen

30
Q

What is an example of an isotope and how is it used?

A

Carbon-14 (radioactive isotope)
It can be used to find the approx. age of an object containing organic material. You calculate the % of C-14 in the object and using the known starting value of carbon (which is the same for all living things) and its half-life to calculate its approx. age

31
Q

Why do nuclei decay to become more stable?

A

they decay to emit radiation because they have too many protons/neutrons which causes the SNF to not be strong enough to keep them stable

32
Q

How were neutrinos discovered?

A

they were first hypothesised because when analysing the energy levels of the particles before and after beta minus decay, they were not the same, so the neutrino was hypothesised to make up for that difference in energy, then they were later discovered

33
Q

What is a neutrino?

A

it is a lepton with no charge and (almost) zero mass

34
Q

What is the value of planck’s constant and the speed of light?

A
  1. 63 x 10⁻³⁴ Js =h

3. 00 x 10⁸ ms⁻¹ = c

35
Q

If photon has more than twice the rest energy of a particle during pair production, then what happens to the remaining energy?

A

it is used as kinetic energy of the particles

36
Q

What are the 4 fundamental forces?

A

gravity
electromagnetic
strong nuclear force
weak nuclear force

37
Q

What are exchange particles?

A

particles that carry momentum and energy between particles experiencing a force
(forces between particles are caused by exchange particles)

38
Q

What is the analogy for describing repulsion?

A

two people on an ice-rink throwing a heavy ball (facing each other)
as the ball is being thrown, it carries momentum which causes the 2nd person to move back

39
Q

What is the analogy for describing attraction?

A

two people on an ice-rink facing away from each other and one throws a boomerang
the boomerang carries momentum to the other person and pushes them both closer together

40
Q

What is the exchange particle for the strong nuclear force and its range ?
What particles does the SNF act on?

A

exchange particle: gluon
range: 3 x 10⁻¹⁵m
acts on: hadrons

41
Q

What is the exchange particle for the weak nuclear force and its range ?
What particles does the WNF act on?

A

exchange particle: W boson (W⁺ or W⁻)
range: 10⁻¹⁸m
acts on: all particle

42
Q

What is the exchange particle for electromagnetism and its range ?
What particles does electromagnetism act on?

A

exchange particle: virtual photon (γ)
range: infinite
acts on: all charged particles

43
Q

What is the exchange particle for gravity and its range?

What particles does gravity act on?

A

exchange particle: graviton (but its not on the spec)
range: infinite
acts on: all particles that have a mass

44
Q

What interactions is the weak nuclear force responsible for? (3)

A
  1. beta decay
  2. electron capture
  3. electron-proton collisions
45
Q

What is electron capture (and draw its Feynman diagram)?

A

when a nucleus captures one of the orbiting electrons and a proton changes into a neutron
Feynman diagram: W+ boson (from proton to neutron/ left to right)
proton and electron at bottom
neutron and neutrino at top (respectively)

46
Q

What is the general term for an exchange particle?

A

boson

47
Q

Draw the Feynman diagram for beta minus decay?

A

neutron at bottom
proton on top
W- boson
e and antineutrino on right top

48
Q

What 2 categories can all particles be placed in?

A

hadrons and leptons

49
Q

What are leptons?

List 3 examples

A

they are a type of fundamental particle
does NOT experience strong force
e.g- electrons and neutrinos and muons

50
Q

What does it mean to be a fundamental particle?

A

cannot be broken down into anything smaller

51
Q

What are hadrons?

List 4 examples

A
  • are made up of quarks (not fundamental particles)
  • experience the strong nuclear force
  • this group can be further divided into baryons or anti baryons or mesons
    e. g- protons, neutrons, pions, kaons
52
Q

What are baryons?

A
  • made up of 3 quarks/antiquarks
  • decays into protons
  • protons, neutrons
53
Q

What are mesons?

A
  • made up of a quark and antiquark
  • does not decay into a proton
  • e.g- pion, kaon
54
Q

What are baryon numbers?

A

it is a property of a particle that shows whether it is a baryon (1) or an antibaryon (-1) or not a baryon at all (0)
the baryon number is always CONSERVED in particle interactions

55
Q

What is the only stable baryon and what happens to the other particles?

A

a proton

all other baryons eventually decay into a proton

56
Q

What is are lepton numbers?

A

shows whether a particle is a lepton (1), an antilepton (-1) or not a lepton at all (0)
lepton numbers are always CONSERVED in particle interactions
2 types of lepton numbers: electron neutrino, muon neutrino

57
Q

What are the two types of lepton numbers?

A

electron lepton numbers

muon lepton numbers

58
Q

What is a muon?

A

it is a lepton, a heavy electron
-1 charge but x200 the mass of an electron
they decay into electrons

59
Q

What are strange particles and an example?

A

they are produced by the strong force but they decay by the weak interaction
e.g- kaons

60
Q

What is strangeness?

A

a property of particles
strange particles must be produced in pairs
strangeness is conserved in strong interactions
in weak interactions, strangeness can change by 0, +1 or -1

61
Q

How can particles be investigated?

A 
cloud chambers
particle accelerators (but they are very expensive)
62
Q

Draw the Feynman diagram for:

  1. beta minus decay
  2. beta plus decay
  3. electron capture
  4. electrostatic repulsion
  5. electron-proton collision
A 
see wall for answers
5. proton (bottom left)
electron (bottom right)
exchange particle= W-
neutron= top left
electron neutrino= top right
63
Q

What happens to a positron straight after pair production?

A

it will meet its antiparticle (electron) and it will annihilate

64
Q

What particle is responsible for mass?

A

Higgs boson

A-level AQA Physics (9 decks)

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