CGP AS Section 1 - Particles Flashcards
1
Q
What are atoms made up of?
A
Protons
Neutrons
Electrons
2
Q
Where are the constituents of an atom located?
A
- protons and neutrons in the nucleus
- electrons orbiting the nucleon core
3
Q
What are nucleons?
A
protons and neutrons
4
Q
What is the relative charge and mass of a proton?
A
relative charge: +1
relative mass: 1
5
Q
What is the relative charge and mass of a neutron?
A
relative charge: 0
relative mass: 1
6
Q
What is the relative charge and mass of a electron?
A
relative charge: -1
relative mass: 1/2000
7
Q
What is the proton number?
A
The proton number is the number of protons in the nucleus of an atom
-it defines the element, no two elements will have the same one
8
Q
What does the proton number of an atom tell you?
A
- the number of electrons in a neutral atom
- so it tells you a lot about its chemical properties cause electrons determine the chemical behaviour of an atom
9
Q
What is the nucleon number?
A
the total number of protons and neutrons
-the number of nucleons is the same as the atom’s relative mass
10
Q
What is the symbol of the proton number?
A
Z
11
Q
What is the symbol of the nucleon/mass number?
A
A
12
Q
Define ion:
A
A particle with a different number of electrons to protons
13
Q
Define isotope:
A
Atoms with the same number of protons but different number of neutrons
14
Q
What does changing the number of neutrons in an atom do?
A
- doesn’t affect its chemical properties
- affects the physical properties (e.g. the stability of the nucleus, unstable nuclei may be radioactive and decay)`
15
Q
What can radioactive isotopes be useful for?
A
To see how old stuff is
- all living things contain the same percentage of carbon-14 taken in from the atmosphere
- after they die this amount decreases as carbon-14 decays into stable elements
- scientist can use this to calculate an approximate age of dead organic matter
16
Q
What type of data do scientists use to calculate the approximate age of dead organic matter?
A
ISOTOPIC DATA (amount of each isotope that is present) -to find the percentage of radioactive carbon-14 that is left in an object
17
Q
What is the specific charge of a particle the same as?
A
its charge over its mass
specific charge = charge ÷ mass
18
Q
What is the unit for specific charge?
A
C kg⁻¹
19
Q
What is a fundamental particle?
A
A fundamental particle is one that you can’t break up into anything smaller
20
Q
What are the forces acting on the nucleons in a nucleus?
A
- electrostatic forces
- gravitational forces
- strong force
- weak force
21
Q
What are some features of the strong force?
A
- it is an attractive force stronger then the electrostatic force
- very short range (fm range)
- strength quickly falls from 3fm to being neutral at 5fm
- works equally between all nucleons (for protons and neutrons)
- below 0.5fm it is repulsive to stop the nucleons crushing to a point
22
Q
Why do alpha emissions occur?
A
-occur in very big nuclei (e.g. uranium and radium), so they are too big for the strong force to keep them stable
23
Q
What is an alpha emission?
A
a helium nucleus (two protons and two neutrons)
- proton number decreases by two
- nucleon number decreases by four
24
Q
What is the features of alpha particles?
A
- have a very short range (only a few centimeters in air), this can be observed by seeing alpha particle tracks in a cloud chamber
- Geiger counter can also show the short range as the count rate drops of rapidly with a little distance
25
What is a beta-minus emission?
the emission of an electron and an antineutrino
26
Why does beta decay occur?
it happens in isotopes that are unstable due to being 'neutron rich' (having too many more neutrons than protons in their nucleus)
27
What happens during beta decay?
One of the neutrons is changed into a proton
| -so the proton number increases by one and the nucleon number stays the same
28
What does the antineutrino carry when it's released in beta-minus decay?
some energy and momentum
29
How were neutrinos hypothesized?
- observations of beta decay showed there was less energy after than before (which doesn't fit the conservation of energy law)
- Pauli suggested another particle was being emitted too, it had to be neutral (to conserve charge) and had to have zero or almost zero mass (as it had never been detected)
- neutrinos were then observed 25 years later providing evidence for the hypothesis
30
What is the electromagnetic spectrum?
```
radio waves
microwaves
infrared
visible light
ultra violet
x-rays
gamma rays
```
31
What happens the frequency and wavelength when you go from radio waves to gamma rays on the electromagnetic spectrum?
- frequency increases
| - wavelength decreases
32
What is the equation linking frequency and wavelength and the speed of light?
frequency = speed of light ÷ wavelength
33
What does the energy of a photon depend on?
the frequency of the radiation
| -electromagnetic radiation exists as photons of energy
34
What is the difference between a particle and its antiparticle?
-opposite charge
35
What are the similarities between a particle and its antiparticle?
-has same mass and same rest energy
36
What is the relative charge and symbol of a proton?
symbol: p
| relative charge: +1
37
What is the relative charge and symbol of a antiproton?
symbol: p with a bar above it
| relative charge: -1
38
What is the relative charge and symbol of a neutron?
symbol: n
| relative charge: 0
39
What is the relative charge and symbol of a antineutron?
symbol: n with a bar above it
| relative charge: 0
40
What is the relative charge and symbol of a electron?
symbol: e⁻
| relative charge: -1
41
What is the relative charge and symbol of a positron?
symbol: e⁺
| relative charge: +1
42
What is the relative charge, mass and symbol of a neutrino?
symbol: ν (a slanted v with a subscript letter according to the type of neutrino)
relative charge: 0
mass: 0
43
What is the relative charge, mass and symbol of a proton?
symbol: ̅ν (a slanted v with a bar and a subscript letter according to the type of neutrino)
relative charge: 0
mass: 0
44
What can you create antimatter and matter from and why?
antimatter and matter can be created from energy
-this comes from Einstein's special theory of relativity, the rest energy of a particle is just the energy equivalent of its mass (comes from E = mc²)
45
What happens when energy is converted into mass?
You get equal amounts of matter and antimatter
46
What is pair production?
When two particles are fired at each other at a high speed, there will be a lot of energy at the point of impact, this energy might be converted to more particles (each in matter and antimatter pairs)
47
When will pair production occur?
if one photon has enough energy to produce that mass, only gamma ray photons have enough energy
-tends to happen near to a nucleus which helps to conserve momentum
48
What is a photon?
energy that gets converted into matter and antimatter is in the form of photon
49
What is the most common pair produced by pair production and how does it travel once it is produced?
- electron-positron pair is the most common (because they have a relatively low mass)
- the particles travel in curved paths as there's usually a magnetic field present, and in opposite direction as they are oppositely charged
50
What is the minimum energy required for a photon to undergo pair production?
the total rest energy of the particles produced
51
What is the opposite of pair production?
annihilation
52
What is annihilation?
When a particle meets its antiparticle and all the mass gets converted back into energy (photons)
53
During annihilation what happens to the energy?
-both photons produced need to have a minimum energy, which when added together equals at least the rest energy of the particles involved added together (for energy to be conserved)
54
What force interactions are explained by exchange particles?
REPULSION
ATTRACTION
-when two particles interact either of these happen to let one particle know the other is there
55
What is another name for an exchange particle?
gauge boson
56
What are the four fundamental forces which cause all forces in nature?
electromagnetic force
gravity
weak nuclear force
strong nuclear force
57
What is the gauge boson for an electromagnetic interaction and what particles does it affect?
Gauge boson: virtual photon
| Particles affected: charged particles only
58
What is the gauge boson for a weak nuclear force interaction and what particles does it affect?
Gauge boson: W⁺ and W⁻
| Particles affected: all types
59
What is the gauge boson for a strong nuclear force interaction and what particles does it affect?
Gauge boson: pions ( π⁺ and π⁻ and π⁰)
| Particles affected: hadrons only
60
Why do particle physicists not bother about gravity?
- it is feeble in comarison to other interactions
| - gravity only really matters when you have big massess
61
What are the two types of gauge bosons for strong force and what are their jobs?
PIONS - exchanges between nucleons
GLUONS - exchanges between quarks
62
What is the relationship between the mass of a gauge boson and the range of the force?
larger mass causes a shorter range
- W bosons have about 100 times the mass of a proton and so have a very short range
- a virtual photon has zero mass and so it has an infinite range
63
What diagrams can you draw to show particle interactions and what are some general rules?
Feynman Diagrams
- gauge bosons are represented by wiggly lines slanted up and with an arrow showing direction
- other particles shown by a straight line and arrows
- incoming particles start at the bottom and move up
- baryons and leptons are on separate sides
- charges on both sides need to balance (W bosons can carry charge from one side to the other)
64
Describe a Feynman diagram for electromagnetic repulsion:
(can be for electrons or positrons)
- has a virtual photon as the exchange particle
- has a lepton line up on either side of the gauge boson squiggle (so 4 lepton lines are labelled)
65
Describe a Feynman diagram for electron capture:
- it is a weak interaction
- has a proton and electron coming from below then a W⁺ boson with the arrow going from the boson to the lepton side
- has a neutron and a neutrino coming out from above that
66
Describe a Feynman diagram for electron-proton collisions:
- it is a weak interaction
- has a proton and electron coming from below then a W⁻ boson with the arrow going from the lepton to the boson side
- has a neutron and a neutrino coming out from above that
67
Describe a Feynman diagram for Beta-plus decay:
n --> p + e⁺ + neutrino
- has a W⁺ boson for exchange
- only has a neutron below and then a proton on the boson side and both a positron and a neutrino coming out of the lepton side with nothing below
68
Describe a Feynman diagram for Beta-minus decay:
p --> n + e⁻ + antineutrino
- has a W⁻ boson for exchange
- only has a proton below and then a neutron on the boson side and both a electron and a antineutrino coming out of the lepton side with nothing below
69
What is the nucleus of an atom made up of?
Protons and neutrons
70
What force holds protons together since they are all positively charged and so should repel each other?
Strong nuclear force or the strong interaction
71
What particle can and can't feel the strong nuclear force?
can - hardrons
| can't - leptons
72
What particles are fundamental and what aren't?
fundamental - leptons
| non-fundamental - hadrons
73
What are hadrons made up of?
quarks
74
What are the two types of hadrons?
- baryons and anti-baryons
| - mesons
75
What determines which type of hadron a particle is?
the number of quarks that make them up
76
What particles are called nucleons?
Protons and neutrons
