Particles Flashcards
(69 cards)
1
Q
What is a fundamental particle?
A
A particle that cannot be broken down any further
2
Q
What are the properties of up quarks?
A
Charge: +2/3
Strangeness: 0
3
Q
What are the properties of down quarks?
A
Charge: -1/3
Strangeness: 0
4
Q
What are the properties of strange quarks?
A
Charge: -1/3
Strangeness: -1
5
Q
What are the properties of anti-up quarks?
A
Charge: -2/3
Strangeness: 0
6
Q
What are the properties of anti-down quarks?
A
Charge: +1/3
Strangeness: 0
7
Q
What are the properties of anti-strange quarks?
A
Charge: +1/3
Strangeness: +1
8
Q
What are protons made of?
A
3 quarks: uud
[electron is a fundamental particle]
9
Q
What are neutrons made of?
A
udd quarks
10
Q
What is the definition of specific charge?
A
The charge per unit mass for a particle
11
Q
What is the definition of Isotope?
A
Different versions of the same element; has SAME number of PROTONS but DIFFERENT number of NEUTRONS
12
Q
What is the strong nuclear force and what are its features?
A
Keeps nucleus stable
Features:
-Short range attraction of 3fm
-Repulsion range of 0.5 fm
[freeform]
13
Q
What happens in Beta+ emissions?
A
-Unstable proton turns into a neutron (weak nuclear force causes a change in quark structure)
-positron and neutrino are emitted to conserve charge and energy
[Beta+ emissions is not natural; they’re manmade]
14
Q
What happens in Beta- emissions?
A
-Unstable neutron turns into a proton (weak nuclear force causes a change in quark structure)
-electron and anti-neutrino are emitted to conserve charge and energy
[they have nearly zero mass and charge]
15
Q
What happens after alpha decay?
A
Gamma radiation is produced
16
Q
What are gauge bosons?
A
aka exchange particles; they’re particles that mediate forces
17
Q
What are the gauge bosons?
A
- gluon - the strong nuclear force
- Photon- Mediates EM force
- W+,W-,Z^0 - the weak nuclear force
- graviton - for gravity
- Mesons (Pions and kaons)
18
Q
What are leptons?
A
‘The light ones’ , they’re all fundamental and it contains 3 families:
-Electron family
-Tau family
-Muon family
19
Q
What are the particles in the electron family?
A
- e- -electron
- Ve- neutrino
- Ve- - anti neutrino
- e+ - positron
20
Q
What are the particles in the Tau family?
A
- tauons: (τ-)
- anti-tau neutrino: (ν̄ₜ)
- anti-tauons: (τ+)
- tau neutrino: (νₜ)
21
Q
What are the particles in the muon family?
A
- Muon: (μ-)
- anti-muon neutrino: (ν̄ₘ)
- anti muon: (μ+)
- muon neutrino: (νₘ)
22
Q
What are hadrons?
A
‘The heavy ones’ and has 2 families:
Baryons and Mesons
23
Q
What are mesons made from?
A
A quark and an anti-quark
24
Q
What are the particles in Mesons?
A
Pions and Kaons
25
What are the symbols for pions?
1. π0 = neutral pions
2. π+ = positively charged pions
3. π- = negatively charged pions
26
What are the symbols for kaons?
-k+= postively charged kaon
-K- = negatively charged kaon
- k^0= neutral kaon
- k-^0= negatively charged neutral kaon?
27
What are baryons made from?
3 quarks or anti-quarks
28
What particles are in the baryon family?
Protons
Neutrons
Lamda
Sigma
Omega
29
What are the symbols for the baryon family?
Proton: P, P- (anti-proton)
Neutron: N, N- (anti-neutron)
Omega: [Ω-]
Lamda: [Λ⁰] [Λ̄⁰] (anti-lamda)
Sigma: Σ⁺,Σ⁰,Σ⁻
30
How do omega, sigma and lamda come to existence?
Only exist during high energy environments eg cosmic rays, particle accelerator ;only exist for a fraction of a second
31
What are quanta?
Photons which carry a quantity of energy
32
How to go from eV to J?
To go from electron volts to joules, you multiply the value by 1.6 x 10^-19
33
What is pair production?
It's when during an even that causes energy to turn into mass [possible coz of e=mc^2] you get equal matter and anti-matter
34
What are the requirements for pair production?
You need enough energy to create the particle and its corresponding anti-particle
[Particles and their corresponding antiparticles have the exact same properties but just different charge]
35
What is annihilation?
When a particle meets its antiparticle
In layman's terms it explodes
all mass is converted into energy [2 gamma ray photons]
36
How do you detect particles using a cloud chamber?
One way is using a cloud chamber. The cloud chamber is filled with alcohol saturated gas ; there's a strong magnetic field which curves the path of particles which we can use to detect charge. This exploits the ionisation effect of the saturated material making liquid condense which leaves a trail.
37
How do you detect particle using a bubble chamber?
The bubble chamber is filled with superheated liquid hydrogen ; there's a strong magnetic field which curves the path of particles which we can use to detect charge. This exploits the ionisation effect of the saturated material making liquid condense which leaves a trail.
38
What needs to be conserved during particle interaction?
Momentum, Lepton number, Baryon number , Strangeness and Charge
[if just one of these are not conserved then the interaction cannot happen]
39
What must a baryon number add up to?
Either 1 or -1
[all quarks and antiquarks have a baryon number{leptons don't coz they're fundamental particles}]
40
Does strangeness always need to be conserved?
No; In interactions involving the strong nuclear force , strangeness MUST be conserved whereas in weak interactions strangeness CAN be conserved , or it can change by +-1
41
Which quarks have strangeness?
ALl quarks/anti-quarks have strangeness=0
Only the strange and anti-strange quark has strangesness
[strange= -1] [anti-strange= 1]
42
What are examples of weak interactions?
Beta decay and Beta+ decay
[weak interactions can also be indicated by a change in quark structure]
43
How does baryon numbers work?
Quarks themselves do not have baryon numbers, however when three of them make a particle, then that particle has a baryon number of +1 and vice versa. However, there needs to be three, Therefore because mesons have a quark and antiquark then it wouldn't have a baryon number. Furthermore, leptons are fundamental particles therefore, they're not composed of quarks thus they have no baryon number.
44
What are Feynman diagrams?
A way to illustrate interactions between particles
45
What do wavy lines in Feynman diagrams represent?
The actual exchange of particles therefore the gauge bosons; it does this by connecting the straight lines
46
What do straight lines in Feynman diagrams represent?
Represents the fermions* before and after particle interaction
Fermions* = anything that’s NOT gauge bosons
47
What is electron capture?
When a proton in the nucleus ‘captures’ an electron and causes it to convert intonation a neutron, which also releases a neutrino.
As a result, the nucleus loses one proton, which decreases the atomic number by 1, whilst the mass number remains unchanged; element becomes an isotope
48
How does the conversation of energy apply to electron capture?
It can only occur if the the energy before the electron has been captured, is less than the energy released when a proton is converted into a neutron
(Because neutrons are lighter than protons)
49
What is the photoelectric effect?
A phenomenal where electrons are emitted from a metal when it’s exposed to light
(1 photon : 1 electron)
50
What are the conditions for photoelectric effect to occur?
1. The energy of photon must exceed the work function
2. Must be at least the threshold frequency of that material
51
What is the work function?
The energy needed to remove an electron from the material
Work function is different for every metal
52
What is the threshold frequency?
The minimum frequency of light by which electrons can be emitted (this is different for every material)
Anything below wouldn’t emit any electrons regardless of the intensity of light. However, increasing intensity of light at the correct frequency increases the effect
53
What are energy levels?
The specific energies that electrons can have when bound to an atom ; electrons can only exist in these energy levels.
Each energy level is specific to their element
54
What are excited states?
When an electron absorbs energy it can move to a higher energy level known as an excited state.
This energy comes from thermal energy or photon absorption
55
What is the ground state?
The lowest energy level of an electron (most stable atp)
56
What is ionisation?
The energy required to remove one electron from an atom
57
How does ionisation work?
The electron must absorb the amount of energy equal to or greater than the ionisation energy. When this happens, the electron is no longer bound to the nucleus
58
How can an electron move to a higher energy level?
By absorbing a photon with energy equal to the difference between two levels
59
How does an electron go to a lower energy level?
Releases the energy in the form of a photon. The energy of the photon emitted is equal to the difference between the two energy levels
60
What are electron Volts?
eV is a unit of energy in particles because the energy scales involved in atoms are very smaller when measured in joules. This allows to us to work with more manageable numbers
61
What is wave-particle duality?
The concept that light can behave as a particle and wave
62
What did Einstein propose about light?
That light can be describe as quanta of energy that behave as particles called photons. Electromagnetic waves carry energy in discrete packets (photons)
63
What did wave theorists predict about light?
For a certain frequency of light the energy carried is proportional to the intensity of the beam, energy carried by the light would spread evenly over the wavefront and that the energy absorbed by each electron gradually increases with each wavefront that passes.
As a result, each free electron would gain enough energy to leave the metal if the exposure time was long enough
(This is wrong)
64
What is electron diffraction?
When electrons produce a diffraction pattern when a beam of electrons is directed at a graphite film
65
What is the condition for electron diffraction to occur?
The electrons must be focused through a gap similar in size to their de brogile wavelength
66
What is observed in the electron diffraction experiment?
Diffraction pattern is a series of concentric rings and that having a larger accelerating voltage reduces the diameter of the rings. Whereas a lower accelerating voltage increases diameter of rings
67
What is the de brogile wavelength?
The wavelength associated with a moving particle
68
What did Louis de brogile suggest?
That particles, not just light exhibit wave- like characteristics
( therefore technically everything, even people have a wavelength and thus can diffract)
69
Why is the wavelength of larger objects small?
Because wavelength is inversely proportional to momentum (which is the product of mass and velocity) so as you increase the mass , the momentum increases and thus the wavelength decreases.
As a result the wavelength is so small that it’s basically Immeasurable
