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a-level physics 2021-22 > 2. Particles & Radiation > Flashcards

2. Particles & Radiation Flashcards

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1
Q

Relative mass of a proton?

A

1

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2
Q

Relative mass of an electron?

A

0

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3
Q

Relative mass of a neutron?

A

1

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4
Q

Relative charge on a proton?

A

1

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5
Q

Relative charge on a neutron?

A

0

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6
Q

Relative charge on an electron?

A

-1

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7
Q

What is the nucleon number?

A

Number of protons + number of neutrons

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8
Q

What letter can be used to represent the nucleon number?

A

A

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9
Q

What are isotopes?

A

Atoms with a different number of neutrons, but the same number of protons

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10
Q

What is a radioisotope?

A

An isotope that is radioactive

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11
Q

What is carbon 14 used in?

A

Carbon dating

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12
Q

What is the specific charge of a nucleus or ion?

A

Its charge per unit mass

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13
Q

What is specific charge used in?

A

Mass spectrometry to identify nuclei

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14
Q

How to calculate specific charge?

A

Charge / mass

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15
Q

Units for specific charge?

A

Ckg⁻¹

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16
Q

What is each type of nucleus called?

A

A nuclide

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17
Q

What is the range of the strong force?

A

3-4 fm (small)

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18
Q

What is 1 fm in m?

A

10⁻¹⁵ m

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19
Q

What does the strong force act between?

A

Nucleons (e.g. protons and neutrons)

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20
Q

Is the strong force attractive or repulsive?

A

Both

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21
Q

Why is the strong force both attractive and repulsive?

A

Otherwise the nucleus would collapse or explode

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22
Q

When is the strong force attractive?

A

> 0.5 fm

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23
Q

When is the strong force repulsive?

A

< 0.5 fm

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24
Q

For light nuclei, what is the ratio of neutrons to protons?

A

Proton number = neutron number → the two particles must exist together

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25
Q

For heavy nuclei, what is the ratio of neutrons to protons?

A

More neutrons than protons (and very large nuclei and radioactive)

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26
Q

What is equilibrium separation?

A

A point when the resultant force is zero and the attractive and repulsive forces balance

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27
Q

What is the decay of americium-241 used for?

A

Smoke alarms

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28
Q

What is the decay of polonium-210 used for?

A

Ionisers

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29
Q

What force is responsible for beta decay?

A

The weak force

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30
Q

How strong is the weak force?

A

1 millionth the value of the strong force

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31
Q

How does the range of the weak force compare to that of the strong force?

A

It has a smaller range

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32
Q

What does the weak force act on?

A

Leptons and hadrons

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33
Q

What are the types of beta decay?

A

β+ and β-

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34
Q

When does beta decay occur?

A

When the nucleus emits an electron or a positron

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35
Q

What does a free neutron decay into in beta decay?

A

A proton, an electron and an anti-neutrino

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36
Q

What does a free proton decay into in beta decay?

A

A neutron, a positron and a neutrino

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37
Q

What type of beta decay is it when a free neutron decays into a proton?

A

β-

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38
Q

What type of beta decay is it when a free proton decays into a neutron?

A

β+

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39
Q

Why it called β- decay when a neutron decays into a proton?

A

An electron is produced

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40
Q

Why is it called β+ decay when a proton decays into a neutron?

A

A positron is produced

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41
Q

What are the energies of the particles emitted in beta and alpha decay?

A
  • beta decay - beta particles emitted have a range of energies
  • alpha decay - monoenergetic
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42
Q

What happens to the unaccounted-for energy in beta decay?

A

It is carried away by the neutrinos

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43
Q

What happens if the nucleus is still unstable after emitting alpha or beta radiation?

A

It is in an excited state, and gives off gamma radiation

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44
Q

What type of wave is gamma?

A

Electromagnetic

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45
Q

What is the mass and charge of gamma?

A

Has no mass or charge

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46
Q

What does the strong force overcome?

A

The electrostatic forces of repulsion between protons in the nucleus

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47
Q

Why was the existence of the neutrino hypothesised?

A

To account for conservation of energy in beta decay

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48
Q

What type of particle are neutrinos?

A

Leptons

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49
Q

What does an electromagnetic wave consist of?

A

An electric wave and a magnetic wave which travel together in phase

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50
Q

When are electromagnetic waves emitted?

A

When a charged particle loses energy

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51
Q

When can a charged particle lose energy (and an electromagnetic wave emitted as a result)?

A
  • when a fast moving electron is stopped, slows down or changes direction
  • when electrons move to a lower energy shell
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52
Q

In what form is electromagnetic radiation emitted?

A

Photons - bursts or packets of energy

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53
Q

How do photons travel?

A

In one direction only in a straight line

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54
Q

What happens to an atom’s energy when it emits a photon?

A

Its energy changes by an amount equal to the photon energy

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55
Q

What is the amount of energy contained in each quantum proportional to?

A

The frequency of the radiation

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56
Q

What is the energy of a photon given by?

A

E = hf

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57
Q

What is ‘h’ in E=hf?

A

The Planck constant

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58
Q

What is the Planck constant measured in?

A

joule-seconds, Js

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59
Q

What is photon energy usually given in?

A

Electron-volts (eV)

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60
Q

What is one electron volt defined as?

A

The energy transferred when an electron is moved through a p.d. of 1V

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61
Q

What is the value of 1 eV?

A

1.6 x 10⁻¹⁹ J

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62
Q

What was Dirac’s theory about particles and antiparticles?

A

For every type of particle, there is a corresponding antiparticle that:

  • annihilates the particle and itself if they meet, converting total mass to photons
  • has same rest mass and opposite charge
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63
Q

When does annihilation occur?

A

When a particle and its corresponding antiparticle meet and their mass is converted into radiation energy

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64
Q

What can the rest energy of an antiparticle be calculated from?

A

By using the rest mass of the colliding particles and E=mc²

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65
Q

What is pair production?

A

When a photon with enough energy can change into a particle antiparticle pair

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66
Q

What is minimum energy required by the photon in pair production?

A

The rest energy of the particle pair

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67
Q

What are the four fundamental interactions?

A
  • strong
  • electromagnetic
  • weak
  • graviational
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68
Q

What is the exchange particle for strong interaction?

A
  • gluon (for quarks)

* pion (for nucleons)

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69
Q

What is the exchange particle for electromagnetic interaction?

A

Photon

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70
Q

What is the exchange particle for weak interaction?

A

W boson

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71
Q

What is the exchange particle for gravitational interaction?

A

Graviton

72
Q

Generally, what happens when two particles interact?

A

They exert equal and opposite forces on each other

73
Q

What happens if two protons approach each other?

A

They repel and move away

74
Q

Why do protons repel when they approach each other?

A

Due to the exchange of a virtual photon

75
Q

What would happen if we tried to intercept virtual photons?

A

We would stop the exchange from happening

76
Q

What is the interaction model of repulsive forces?

A

Two people on skateboards facing each other - throwing a ball between them causes them to move away from each other

77
Q

What is the interaction model of attractive forces?

A

Two people on skateboards - throw a boomerang and momentum causes them to move towards each other

78
Q

In interaction diagrams, what do the straight and wavy lines represent?

A
  • the lines do NOT represent the paths of the particles

* the wavy line shows the exchange particle

79
Q

What must be conserved in interaction diagrams?

A

Charge, lepton and baryon number

80
Q

Describe the interaction diagram between two protons.

A
  • lines show protons approaching
  • wavy line shows virtual photon as the exchange particle
  • then shows that protons move away
81
Q

Describe the interaction diagram between a neutron and a neutrino.

A
  • lines show neutron and neutrino approaching
  • wavy line shows W⁻ boson as the exchange particle
  • then shows that a proton and an electron move away
82
Q

Describe the interaction diagram between a proton and an anti-neutrino.

A
  • lines show proton approaching an anti-neutrino
  • wavy line shows W⁺ boson as the exchange particle
  • then shows that a neutron and a positron move away
83
Q

Describe the interaction diagram for electron capture.

A
  • lines show a proton and electron approaching each other
  • wavy line shows W⁺ boson as the exchange particle
  • then shows that a neutron and a neutrino move away
84
Q

Describe the interaction diagram for β- decay.

A
  • line shows neutron
  • wavy line shows W⁻ boson as the exchange particle
  • then shows that a proton, electron and anti-neutrino move away
85
Q

Describe the interaction diagram for β+ decay.

A
  • line shows proton
  • wavy line shows W⁺ boson as the exchange particle
  • then shows that a neutron, positron and neutrino move away
86
Q

What is the process of electron capture?

A

When a proton in a proton-rich nucleus turns into a neutron, as a result of interacting with an inner shell electron from outside the nucleus

87
Q

Why can’t strong or electromagnetic interaction be responsible for beta decay?

A
  • strong force holds neutrons and protons in a nucleus together, but doesn’t cause neutron to change into proton
  • electromagnetic force only when a charged particle loses energy → neutron not charged
88
Q

What do leptons exist as?

A

Particles on their own

89
Q

What do quarks exist as?

A

Only exist bound together

90
Q

Examples of leptons?

A
  • electron
  • electron neutrino
  • muon
  • tau
91
Q

Which leptons are constituents of ordinary matter (1st family)?

A
  • electons

* electron neutrinos

92
Q

Which leptons are only found in cosmic rays and particle accelerators?

A
  • muon
  • muon neutrino
  • tau
  • tau neutrino
93
Q

Charge on an electron neutrino?

A

0

94
Q

Which quarks are part of the 1st family?

A
  • up

* down

95
Q

Which quarks are part of the 2nd family?

A
  • charm

* strange

96
Q

Which quarks are part of the 3rd family?

A
  • top

* bottom

97
Q

Which quarks are protons made up of?

A

Two up quarks and one down quark

98
Q

Which quarks are neutrons made up of?

A

One up quark and two down quarks

99
Q

Which quarks are antiprotons made up of?

A

Two antiup quarks and one antidown quark

100
Q

What is the charge on an up quark?

A

+ 2/3

101
Q

What is the charge on a down quark?

A
  • 1/3
102
Q

What is the charge on an antiup quark?

A
  • 2/3
103
Q

What is the charge on an antidown quark?

A

+ 1/3

104
Q

What is a muon?

A

A heavier relative of the electron

105
Q

What is the charge on a muon?

A

-1

106
Q

What is a tau?

A

A heavier relative of the electron and muon

107
Q

What is the charge on a tau?

A

-1

108
Q

What is a strange particle?

A

A heavier relative of the down quark

109
Q

What are hadrons?

A

Particles that feel the strong force

110
Q

How do hadrons decay?

A

Weak interaction

111
Q

What groups are hadrons split into?

A
  • baryons - 3 quarks

* mesons - 2 quarks

112
Q

Are protons and neutrons fundamental? Why is this?

A

No, they are made up of quarks

113
Q

Are protons and neutrons mesons or baryons? Why is this?

A

Baryons - they are made up of three quarks

114
Q

What is the only stable baryon?

A

Protons

115
Q

What is the pion?

A

The exchange particle of the strong nuclear force

116
Q

What do strange particles contain?

A

A strange quark

117
Q

How are strange particles produced?

A

Strong interaction

118
Q

How do strange particles decay?

A

Weak interaction

119
Q

When is strangeness conserved?

A

Only in strong interactions

120
Q

What do Kaons decay into?

A

Pions

121
Q

Do leptons feel the strong force?

A

No

122
Q

What force are leptons affected by?

A

Weak interaction

123
Q

What do muons decay into?

A

Electrons

124
Q

What can leptons and antileptons interact to produce?

A

Hadrons

125
Q

How fast do neutrinos travel?

A

Almost as fast as light

126
Q

How can leptons change into other leptons?

A

Weak interaction

127
Q

Baryon number on up quarks?

A

1/3

128
Q

Baryon number on down quarks?

A

1/3

129
Q

Baryon number on strange quarks?

A

1/3

130
Q

Baryon number on anti-up quarks?

A

-1/3

131
Q

Baryon number on anti-down quarks?

A

-1/3

132
Q

Baryon number on anti-strange quarks?

A

-1/3

133
Q

Strangeness of an up quark?

A

0

134
Q

Strangeness of a down quark?

A

0

135
Q

Strangeness of a strange quark?

A

-1

136
Q

Strangeness of an anti-strange quark?

A

1

137
Q

What do mesons consist of?

A

A quark and an antiquark

138
Q

What do pions consist of?

A

Up and down quarks

139
Q

What do kaons consist of?

A

A strange quark and either an up or down quark

140
Q

What charge can pions have?

A

Zero charge, or positively/negatively charged

141
Q

What are the kaon combinations?

A
  • strange-antiup (-1)
  • strange-antidown (0)
  • antistrange-up (1)
  • antistrange-down (0)
142
Q

When does beta decay occur?

A

When the nucleus emits an electron or a positron

143
Q

What is conserved in beta decay?

A

Charge, spin, baryon number and lepton number

144
Q

What else needs to be conserved (along with charge, spin, baryon and lepton no.) in particle reactions?

A

Energy and momentum

145
Q

What is photoelectric emission?

A

The emission of electrons from the surface of a metal when it is exposed to electromagnetic radiation of sufficiently high frequency

146
Q

In photoelectric emission, what is the rate of electrons emitted proportional to?

A

Rate of electrons is directly proportional to the intensity of the radiation

147
Q

What kinetic energy are photoelectrons emitted with?

A

A range of kinetic energies (the max. ↑ with f, and is independent of intensity)

148
Q

What is threshold frequency in photoelectric emission?

A

The minimum frequency to produce emission

149
Q

Why, when a photon causes an electron to be ejected from the surface of the metal, is the energy of the electron always less than that of the incident photon?

A

Energy from the photon is used to remove the electron

150
Q

What is the work function?

A

The minimum energy needed by an electron to escape from the metal surface

151
Q

Symbol for work function?

A

Φ

152
Q

Equation for work function?

A

Φ = hf₀ (where f₀=threshold frequency)

153
Q

What type of energy does a photo-electron have when it has absorbed a photon and escaped from the metal?

A

Kinetic

154
Q

Equation to calculate maximum KE of photo-electrons?

A

KEₘₐₓ = hf - Φ

155
Q

What is stopping potential?

A

The minimum potential needed to stop photoelectric emission

156
Q

At the stopping potential, what is the maximum KE of the emitted electrons?

A

0

157
Q

How are line spectra formed?

A
  • atoms excited by heating or electrical discharge
  • energy raises electrons to higher energy levels
  • when electrons fall back to a lower level there is an energy output
158
Q

Which elements have a line spectra?

A

All of them

159
Q

What happens to the energy of electrons in shells as they get further from the nucleus?

A

Further away from nucleus = higher energy

160
Q

What is the ground state?

A

The lowest energy state of an atom

161
Q

What are excitation energies?

A

The energies at which an atom absorbs energy

162
Q

How can electrons be excited?

A
  • electron collisions - doesn’t have to have exact value to move an electron to the next level
  • photon absorption - only photons with exactly enough energy between energy levels can be absorbed
163
Q

How does a fluorescent tube emit light?

A
  • ionisation and excitation of mercury atoms as they collide with each other and with electrons in the tube
  • mercury atoms emit UV photons
  • UV photons absorbed by fluorescent coating, causing excitation of atoms
  • coating atoms de-excite in steps and emit visible photons
164
Q

What is a fluorescent tube?

A

A glass tube with a fluorescent coating on its inner surface

165
Q

What does a fluorescent tube contain?

A

Mercury vapour at a low pressure

166
Q

Why do energy levels have negative energy values?

A

0 is considered to be that of a free electron just outside the atom, so all the energy states below this are negative

167
Q

How to calculate the increase in energy difference of a transition?

A

hf = E₁ - E₂

168
Q

What is the difference between line spectra and band spectra?

A
  • line spectra - formed by hot gases as atoms in gas isolated and so have minimal interaction
  • band spectra - solids and liquids have atoms close together so interaction between neighbouring atoms means there’s a large number of lines close together so appear to be bands
169
Q

What did De Broglie propose?

A

That electrons, which we thought were particles, can be waves also

170
Q

How does electron diffraction occur?

A
  • beam of electrons strike thin layers of graphite carbon - most pass through, others pass through at certain angles only, giving rings
  • rings like interference maxima (when light waves pass through diffraction grating)
  • this shows electrons are diffracted by the gaps between atoms, and give maxima on the screen when they’re in phase
171
Q

What size did De Broglie suggest that the wavelength of electron waves are?

A

Very small, about the size of an atom

172
Q

How big do the separation of the slits in a diffraction grating for electrons have to be?

A

Very small - about the size of an atom

173
Q

What is De Broglie’s equation?

A

mv = h / λ

174
Q

What is the setup for electron diffraction?

A
  • beam of electrons produced by attracting them from a heated wire filament to a positively charged metal plate
  • plate has a hole in, electrons pass through
175
Q

What changes the size of diffraction rings electron diffraction?

A

An increase in velocity of electrons will decrease de Broglie wavelength and so make the rings smaller

a-level physics 2021-22 (11 decks)

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