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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
Describe the way photons travel after annihilation?
they move in opposite directions and perpendicular to matter/antimatter to conserve momentum
26
What is pair production?
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
What condition is required for pair production to occur?
it only happens if there is enough energy to produce the masses of the particles
28
What is the minimum energy required for pair production?
the total rest energies of the particles that are produced Eₘᵢₙ=2E₀ E₀ is the rest energy of particle type produced
29
What is usually produced from pair production?
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
What is an example of an isotope and how is it used?
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
Why do nuclei decay to become more stable?
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
How were neutrinos discovered?
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
What is a neutrino?
it is a lepton with no charge and (almost) zero mass
34
What is the value of planck's constant and the speed of light?
6. 63 x 10⁻³⁴ Js =h | 3. 00 x 10⁸ ms⁻¹ = c
35
If photon has more than twice the rest energy of a particle during pair production, then what happens to the remaining energy?
it is used as kinetic energy of the particles
36
What are the 4 fundamental forces?
gravity electromagnetic strong nuclear force weak nuclear force
37
What are exchange particles?
particles that carry momentum and energy between particles experiencing a force (forces between particles are caused by exchange particles)
38
What is the analogy for describing repulsion?
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
What is the analogy for describing attraction?
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
What is the exchange particle for the strong nuclear force and its range ? What particles does the SNF act on?
exchange particle: gluon range: 3 x 10⁻¹⁵m acts on: hadrons
41
What is the exchange particle for the weak nuclear force and its range ? What particles does the WNF act on?
exchange particle: W boson (W⁺ or W⁻) range: 10⁻¹⁸m acts on: all particle
42
What is the exchange particle for electromagnetism and its range ? What particles does electromagnetism act on?
exchange particle: virtual photon (γ) range: infinite acts on: all charged particles
43
What is the exchange particle for gravity and its range? | What particles does gravity act on?
exchange particle: graviton (but its not on the spec) range: infinite acts on: all particles that have a mass
44
What interactions is the weak nuclear force responsible for? (3)
1. beta decay 2. electron capture 3. electron-proton collisions
45
What is electron capture (and draw its Feynman diagram)?
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
What is the general term for an exchange particle?
boson
47
Draw the Feynman diagram for beta minus decay?
neutron at bottom proton on top W- boson e and antineutrino on right top
48
What 2 categories can all particles be placed in?
hadrons and leptons
49
What are leptons? | List 3 examples
they are a type of fundamental particle does NOT experience strong force e.g- electrons and neutrinos and muons
50
What does it mean to be a fundamental particle?
cannot be broken down into anything smaller
51
What are hadrons? | List 4 examples
- 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
What are baryons?
- made up of 3 quarks/antiquarks - decays into protons - protons, neutrons
53
What are mesons?
- made up of a quark and antiquark - does not decay into a proton - e.g- pion, kaon
54
What are baryon numbers?
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
What is the only stable baryon and what happens to the other particles?
a proton | all other baryons eventually decay into a proton
56
What is are lepton numbers?
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
What are the two types of lepton numbers?
electron lepton numbers | muon lepton numbers
58
What is a muon?
it is a lepton, a heavy electron -1 charge but x200 the mass of an electron they decay into electrons
59
What are strange particles and an example?
they are produced by the strong force but they decay by the weak interaction e.g- kaons
60
What is strangeness?
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
How can particles be investigated?
``` cloud chambers particle accelerators (but they are very expensive) ```
62
Draw the Feynman diagram for: 1. beta minus decay 2. beta plus decay 3. electron capture 4. electrostatic repulsion 5. electron-proton collision
``` see wall for answers 5. proton (bottom left) electron (bottom right) exchange particle= W- neutron= top left electron neutrino= top right ```
63
What happens to a positron straight after pair production?
it will meet its antiparticle (electron) and it will annihilate
64
What particle is responsible for mass?
Higgs boson

A-level AQA Physics (9 decks)

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