Particles and Radiation Flashcards
Imported 07/03 (144 cards)
1
Q
Charge of a proton/electron
A
1.6x10^-19
2
Q
Mass of proton/neutron
A
1.67x10^-27
3
Q
Mass of electron
A
9.11x10^-31
4
Q
Specific charge formula
A
Charge/mass
5
Q
What are isotopes
A
Atoms with the same number of protons but diff number of neutrons
6
Q
What is carbon dating
A
Calculating percentage of carbon-14 remaining in object, using known starting value (same for all living things) and half life to calculate approximate age
7
Q
What is the strong nuclear force
A
Keeps nuclei stable, counteracts electrostatic force, only acts on nucleons, very short range, attractive up to 3fm, repulsive below 0.5fm
8
Q
What is an unstable nuclei
A
Has too many protons, neutrons or both, strong nuclear force not enough to keep them stable, nueclei will decay to become stable
9
Q
Where and how does alpha decay occur
A
Large nuclei, too many protons AND neutrons, 2 protons, 2 neutrons
10
Q
Where and how does beta minus decay occur
A
When too many neutrons, proton number increases by 1, lose 1 electron
11
Q
What did observation of energy levels in beta decay lead to
A
The discovery of the neutrino
12
Q
Particles and antiparticles common properties
A
Rest energy and mass
13
Q
How does electromagnetic radiation travel
A
In photons
14
Q
What is the energy of photons directly proportional to
A
Frequency
15
Q
Energy and planck constant formulas
A
E = hf = hc/?
16
Q
What is annihilation
A
Particle and corresponding antiparticle collide, masses converted to energy, 2 photons moving in opposite directions are released to conserve momentum
17
Q
Application of annihilation
A
PET scanner - 3D images of inside body taken, introducing positron emitting radioisotope into patient, positrons annihilate, releases gamma photons which can be easily detected
18
Q
What is pair production
A
Photon collides with matter (to conserve momentum) and is converted into equal amount of matter and antimatter, only occurs when photon has energy > total rest energy of both particles, any excess energy is converted to kinetic
19
Q
What are the 4 fundamental forces
A
Gravity, electromagnetic, weak nuclear force, strong nuclear force
20
Q
What are forces between particles caused by
A
Exchange particles
21
Q
What are exchange particles
A
Carry energy and momentum between particles - ball vs boomerang analogy
22
Q
Exhange particle for strong force
A
Gluon
23
Q
Range of strong force
A
3fm
24
Q
What does strong force act on
A
Hadrons
25
Exhange particle for weak force
W boson (+ or -)
26
Range of weak force
10^-18
27
What does weak force act on
All particles
28
Exhange particle for electromagnetic force
Virtual photon (?)
29
Range of electromagnetic force
Infinite
30
What does electromagnetic force act on
Charged particles
31
Exhange particle for gravity
Graviton (theoretical)
32
Range of gravity
Infinite
33
What does gravity act on
Particles with mass
34
Examples of what the weak force is
responsible for
Beta decay, electron capture, electron-proton collisions
35
What causes beta decay, electron capture and electron-proton collisions
Weak force
36
Electron capture formula
p+e=n+Ve
37
Electron-proton collision formula
p+e=n+Ve
38
Exchange particle in electron capture
W+
39
Exchange particle in electron-proton collision
W-
40
Direction of arrow in electron capture
p to e (left to right)
41
Direction of arrow in electron-proton collision
e to p (right to left)
42
Beta plus decay formula
p = n + e^+ +Ve
43
Beta minus decay formula
n = p + e + Ve(anti)
44
Exchange particle in beta plus decay
W+
45
Exchange particle in beta minus decay
W-
46
Direction of arrow in beta plus decay
p to Ve (left to right)
47
Direction of arrow in beta minus decay
n to Ve (left to right)
48
What are leptons
Fundamental particles - do not experience strong nuclear force
49
What are hadrons
Formed of quarks, experience strong nuclear force
50
What are the classifications for fundamental or non-fundamental particles
Hadrons and leptons
51
Subcategories for hadrons
Baryons, antibaryons and mesons
52
What are baryons
Type of hadron, formed from 3 quarks
53
What are antibaryons
Type of hadron, formed from 3 antiquarks
54
What are mesons
Type of hadron, formed from a quark and an antiquark
55
Examples of leptons
Electron, muon, electron neutrino, muon neutrino, (and their antiparticles)
56
Examples of baryons
Proton or neutron
57
Examples of mesons
Pion, kaon
58
Baryon number
1 if baryon, -1 if antibaryon, 0 if not a baryon, conserved in particle interactions
59
What is the only stable baryon
Proton
60
What are special about protons as baryons
Only stable one
61
Why is it important that protons are the only stable baryon
All baryons eventually decay into protons
62
Lepton number
1 if lepton, -1 if antilepton, 0 if not a lepton, 2 types, electron lepton and muon lepton, lepton number always conserved in particle interactions
63
What are muons
Known as heavy electrons, decay into electrons
64
Production and decay of strange particles
Produced by strong nuclear interaction, decay by weak interaction
65
Strange particles example and decay
Kaons decay into pions via the weak interaction
66
Conservation of strangeness
Strange particles must be created in pairs as strangeness must be conserved in strong interactions, in weak interactions, strangeness can change by -1, 0 or 1
67
Investigation of particle physics
Particle accelarators can be used, expensive to build and run, produce huge amounts of data, scientific investigations rely on collaboration of scientists internationally
68
Properties of quarks
Charge, baryon number, strangeness
69
3 types of quarks
Up, down, strange
70
Charge of up
+2/3 e
71
Baryon number of up
+1/3
72
Strangeness of up
0
73
Charge of down
-1/3 e
74
Baryon number of down
1/3
75
Strangeness of down
0
76
Charge of strange
-1/3 e
77
Baryon number of strange
+1/3
78
Strangeness of strange quark
-1
79
How do the charge, baryon number and strangeness of a quark change for antiquarks
Opposite sign
80
Quark combination for ?0
u(anti)u or d(anti)d
81
Quark combination for ?+
u(anti)d
82
Quark combination for ?-
(anti)ud
83
Quark combination for k0
d(anti)s or (anti)ds
84
Quark combination for k+
u(anti)s
85
Quark combination for k-
(anti)us
86
Charge for ?0
0
87
Charge for ?+
1
88
Charge for ?-
-1
89
Charge for k0
0
90
Charge for k+
1
91
Charge for k-
-1
92
Strangeness for ?0
0
93
Strangeness for ?+
0
94
Strangeness for ?-
0
95
Strangeness for k0
+/- 1
96
Strangeness for k+
1
97
Strangeness for k-
-1
98
Equation for neutron decaying into proton
n = p + e + Ve(anti)
99
What properties must always be conserved in particle interaction
Energy and momentum, charge, baryon number, electron lepton number, muon lepton number
100
When is strangeness conserved
During strong interactions
101
What doesn't have to be conserved during decay
Strangeness
102
Why are beta minus and plus decay caused by weak interaction
Because there is a change of quark type
103
Change of quark in beta minus decay
D into U
104
Change of quark in beta plus decay
U into D
105
What is the threshold frequency
Minimum frequency that needs to be shone on a metal for photoelectrons to be emitted from the surface
106
How does the photoelectric effect contradict the wave theory
Wave theory says that any frequency of light should cause photoelectric emission as energy absorbed would gradually increase with each wave
107
How does the photon model of light explain the photoelectric effect
Each electron can absorb a single photon, so photoelectron only emitted if frequency is above the threshold frequency (E=kf), as intensity increases, more photoelectrons are emitted per second
108
What is the work function of a metal
Minimum energy required for electrons to be emitted from the surface of a metal, ?
109
What is the stopping potential
Potential difference that would need to be applied across the metal to stop the photoelectrons with the max kinetic energy
110
What can finding the stopping potential do
Allows you to find the max kinetic energy of the released photoelectrons, E(max kinetic) = eVs - e = charge of electron and Vs = stopping potential
111
Photoelectron equation
E = hf = ? + E(max kinetic)
112
How does the energy of electrons in atoms work
Discrete energy levels
113
What is it called when an electron moves up an energy level
Excitation
114
How can electrons gain the energy to move up an energy level
Via collisions with free electrons
115
What happens when an electron in an atom gain energy
Excitation or being removed from the atom entirely
116
What is it called when an electron is removed from the atom
Ionisation
117
What condition has to be met for ionisation to occur
Energy of free electron > ionisation energy
118
What happens after an electron gets excited and moves up a level
Quickly returns to original energy level (ground state), so releases energy it gained in the form of a photon
119
Example of a practical use of excitation
In a fluorescent tube to produce light, tube filled with mercury vapour, high voltage applied across it, voltage accelerates free electrons through tube, collide with mercury atoms which become ionised, releasing more free electrons, cause mercury atoms to become excited, when they de-excite they release photons, mostly within UV range, fluorescent coating on inside of tube absorbs the photons and so electrons in atoms of coating become excited and de-excite releasing photons of visible light
120
Units for small values of energy
Electron volt
121
What is an electron volt
Energy gained by one electron when passing through a potential difference of 1 volt
122
How many joules are in an electron volt
1.6 x 10^-19
123
What is bigger, electron volt or joule
Joule
124
How to convert from electron volt to joule
x by 1.6x10^-19
125
How to convert from joule to electron volt
Divide by 1.6x10^-19
126
What happens when pass a light from fluorescent tube through diffraction grating or prism
Get a line sprectrum
127
What does each line in a line sprectrum represent
A diff wavelength
128
Is the line spectrum for a fluorescent tube continuous or discrete
Discrete
129
How is a discrete line spectrum evidence for discrete energy levels
The photon energies emitted will correspond to the wavelengths, so evidence that atoms can only transition between discrete energy levels
130
What happens when you pass white light through a cooled gas
Line absorption spectrum
131
How to get a line absorption spectrum
Pass white light through a cooled gas
132
What does a line absorption spectrum look like
Continuous spectrum of all possible wavelengths with black lines at certain wavelengths
133
What do the black lines on a line absorption spectrum represent
Possible differences in energy levels - atoms can only absorb photons of an energy equal to exact difference between two energy levels
134
Change in energy formula using discrete energy lines
?E = E1 - E2 where E1 and E2 are energy levels so hf = E1 - E2
135
What 2 properties can light be shown as having
Wave and particles
136
Examples of light acting as a wave
Diffraction, interference
137
Example of light acting as a particle
Photoelectric effect
138
De Broglie's equation linking momentum and wavelength
wavelength = h/mv
139
What happens to the wavelength and diffraction when the momentum is increased
Both decrease
140
What happens to the wavelength and diffraction when the momentum is decreased
Both increase
141
How does knowledge and understanding of any scientific concept change over time
In accordance to the experimental evidence gathered by scientific community
142
Does knowledge and understanding of scientific concepts change over time
YES
143
What must happen to experimental evidence before it is accepted
Be published to allow for peer-review by scientific community to become validated
144
Why is the weak force responsible for decay
Change of quark
