Particles And Radiation Flashcards
(111 cards)
1
Q
What is the relative mass of a proton?
A
1
2
Q
What is the relative mass of a neutron?
A
1
3
Q
What is the relative mass of an electron?
A
1/2000 or negligible
4
Q
What is the relative charge of a proton?
A
+1
5
Q
What is the relative charge of a neutron?
A
0
6
Q
What is the relative charge of an electron?
A
-1
7
Q
What is the overall charge of an atom?
A
Neutral or zero
8
Q
What is the overall charge of a nucleus?
A
Positive
9
Q
What is the approximate size of an atom?
A
1 x 10^-10 m
10
Q
What is the approximate size of a nucleus?
A
1 x 10^-15 m
11
Q
What is found between the nucleus and electrons?
A
Empty space
12
Q
In A-Z nuclide notation, what does A represent?
A
Nucleon number
13
Q
In A-Z nuclide notation, what does Z represent?
A
Proton number / atomic number
14
Q
Which number, A or Z, defines which element it is?
A
Z (proton/atomic number)
15
Q
What is the definition of nucleon number?
A
Total number of protons and neutrons
16
Q
Complete: atoms have equal number of… and …
A
Protons and electrons
17
Q
How do atoms become positive ions?
A
They lose electrons
18
Q
How do atoms become negative ions?
A
They gain electrons
19
Q
What is the magnitude of the charge on an electron/proton?
A
1.60 x 10^-19 C
20
Q
What is the mass of a nucleon?
A
1.67 x 10^-27 kg
21
Q
What is the mass of an electron?
A
9.11 x 10^-31 kg
22
Q
How do we work out the mass of an atom, ion or nucleus in kilograms?
A
Number of nucleons x 1.67 x 10^-27
23
Q
How do we work out the charge of a nucleus in coulombs?
A
Number of protons x 1.60 x 10^-19
24
Q
How do we work out the charge of an ion in coulombs?
A
Relative charge x 1.60 x 10^-19
25
How do we calculate specific charge?
Specific charge = charge / mass = Q / m
26
What are the units for specific charge?
C kg^-1
27
What are isotopes?
Atoms with the same number of protons and different numbers of neutrons
28
True or false: isotopes have different chemical properties.
False
29
True or false: isotopes have different nuclear stability.
True
30
What role does the strong nuclear force play in nuclear stability?
Balances the electrostatic repulsion between positively charged protons and holds nucleons in equilibrium
31
Is the strong nuclear force associated with charge?
No
32
Describe the strength of the nuclear force with nuclear separation.
Below 0.5 fm -> repulsive; Between 0.5 – 3.0 fm -> attractive; Beyond 3.0 fm -> zero
33
What type of nuclei normally undergo alpha decay?
Massive nuclei
34
What is an alpha particle made up of?
2 protons and 2 neutrons (helium nucleus)
35
What type of nuclei normally undergo beta minus decay?
Neutron-rich nuclei (high neutron to proton ratio)
36
What is a beta minus particle?
An electron
37
Describe the change in nucleons during beta minus decay.
A neutron changes into a proton
38
What is the extra particle emitted in beta minus decay?
Electron anti-neutrino
39
Why did scientists hypothesize the extra particle in beta minus decay?
Missing energy must be carried away by another particle to conserve energy
40
Why was it difficult to detect the extra particle in beta minus decay?
It has no mass and no charge
41
What type of nuclei normally undergo gamma decay?
Nuclei that need to lose excess energy
42
What is a gamma ray?
High energy EM wave
43
Which decays lead to the formation of an atom of a different element?
Alpha and beta minus decay because proton number changes
44
What is meant by the duality of EM radiation?
Can behave as a wave or a particle
45
What is a photon?
A discrete packet/quantum of EM energy
46
What units do the equations for photon energy calculate energy in?
Joules
47
What is the Planck constant and its value?
6.63 x 10^-34 Js
48
What is the speed of light and its value?
3.00 x 10^8 ms^-1
49
The energy of a photon is directly proportional to…
Frequency
50
The energy of a photon is inversely proportional to…
Wavelength
51
What is the definition of an electron-volt?
The energy gained by an electron traveling through a potential difference of 1 V
52
How do we convert eV to J?
Multiply by 1.6 x 10^-19
53
How do we convert J to eV?
Divide by 1.6 x 10^-19
54
Give two similarities between particles and anti-particles.
* Rest mass
* Rest energy
55
Give one difference between particles and anti-particles.
Charge
56
What is energy-mass equivalence?
Energy can be converted into mass and mass can be converted into energy, calculated by E= mc^2
57
What happens in pair production?
A gamma photon interacts with a nucleus and creates a particle and anti-particle pair
58
Which pair of particles is most likely to be created in pair production?
Electron and positron
59
Why does it need to be a gamma photon for pair production?
It has the highest energy
60
How can we calculate the minimum energy of the photon required for pair production?
Emin = 2 x rest energy of particle/anti-particle
61
What is the rest energy of an electron/positron?
0.510999 MeV
62
How can you convert MeV into J?
x 10^6 x 1.6 x 10^-19
63
What happens in annihilation?
A particle meets its equivalent anti-particle and their mass is converted into energy in the form of two gamma photons
64
Why are two gamma photons produced in annihilation?
They travel in opposite directions to conserve momentum
65
How can we calculate the minimum energy of one of the photons produced in annihilation?
2 x Emin = 2 x rest energy of particle/anti-particle
66
Why is this the minimum energy of the photon in annihilation?
The particle and anti-particle may have additional kinetic energy
67
What is the role of exchange particles in particle interactions?
Move between particles and give rise to the force between them
68
Name the four fundamental forces from strongest to weakest.
* Strong nuclear force
* Electromagnetic force
* Weak nuclear force
* Gravity
69
Which of the four fundamental forces do particle physicists normally ignore?
Gravity
70
What is the exchange particle for the strong nuclear force?
Pions (π)
71
What is the exchange particle for the electromagnetic force?
Virtual photons (ϒ)
72
What is the exchange particle for the weak nuclear force?
W+ and W- bosons
73
What particles are affected by the strong nuclear force?
Hadrons
74
What particles are affected by the electromagnetic force?
Charged particles
75
What particles are affected by the weak nuclear force?
All particles
76
What is the range of the strong nuclear force?
10^-15 m
77
What is the range of the electromagnetic force?
Infinite
78
What is the range of the weak nuclear force?
10^-18 m
79
Describe the relationship between the mass of the exchange particle and the range of the force.
Larger mass -> shorter range
80
What are two differences between hadrons and leptons?
* Hadrons experience the strong interaction
* Hadrons are made up of quarks
81
Give two examples of baryons.
* Protons
* Neutrons
82
What is the quark structure of baryons?
3 quarks
83
Name the only stable baryon.
Proton
84
What is the baryon number of protons and neutrons?
+1
85
What is the baryon number of antiprotons and antineutrons?
-1
86
What is the quark combination for a proton?
uud
87
What is the quark combination for a neutron?
udd
88
Why do neutrons have a higher mass than protons?
d quark has a higher mass than u quark
89
Give two examples of mesons.
* Pions
* Kaons
90
What is the quark structure of mesons?
A quark and an antiquark
91
True or false: All mesons are unstable.
True
92
Name the most stable meson.
Pions
93
What does strangeness tell you about quark structure?
Kaons contain a strange or anti-strange quark
94
How are kaons produced?
By the strong interaction
95
How do kaons decay?
By the weak interaction
96
Why do kaons have a higher mass than pions?
s quark has higher mass than u and d quarks
97
Give three examples of leptons.
* Electrons
* Muons
* Neutrinos
98
Compare electrons and muons.
* Same charge
* Muons are heavier than electrons
* Electrons are stable, muons decay into electrons
99
What is the mass and charge of neutrinos?
Zero mass and zero charge
100
What are the leptons with Le = +1?
* Electron
* Electron-neutrino
101
What are the leptons with Le = -1?
* Positron
* Electron-anti-neutrino
102
What are the leptons with Lµ = +1?
* Muons
* Muon-neutrino
103
What are the leptons with Lµ = -1?
* Anti-muons
* Muon-anti-neutrino
104
What are the four particle interaction conservation laws?
* Baryon number (B) – always conserved
* Charge (Q) – always conserved
* Lepton number (L) - Le and Lµ always conserved separately
* Strangeness (S) – always conserved in strong interaction
105
State two other quantities that are conserved in all interactions.
* Energy
* Momentum
106
Why are strange particles always produced in pairs?
Strangeness must be conserved
107
In which type of interaction can quark character change?
Weak interaction only
108
What is the change of quark in beta minus decay?
d -> u
109
What is the change of quark in beta plus decay?
u -> d
110
What is quark confinement?
Not possible for quarks to exist in isolation
111
Why does particle physics research rely on collaborative efforts?
Particle accelerators are expensive, requiring collaboration to spread costs
