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AQA A-Level Physics > Particles and radiation > Flashcards

Particles and radiation Flashcards

1
Q

Isotopes

A

Same proton number but different nucleon number

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2
Q

Atomic structure

A

Protons and neutrons in nucleus
Electrons in orbit

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3
Q

Charge of Proton

A

1.6 x 10^-19

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4
Q

Charge of neutron

A

0

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5
Q

Charge of electron

A

-1.6 x 10^-19

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6
Q

Mass of proton

A

1.673 x 10^-27

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7
Q

Mass of neutron

A

1.675 x 10^-27

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8
Q

Mass of electron

A

9.11 x 10^-31

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9
Q

Relative charge of Proton, Neutron and Electron

A

+1 , 0 , -1

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10
Q

Relative mass of Proton, Neutron and Electron

A

1, 1, 0.0005

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11
Q

Specific charge

A

Charge/mass = Ckg^-1

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12
Q

Use of strong nuclear force?

A

Glues the nucleus together
Stronger than electrostatic force (repulsion)

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13
Q

What is alpha decay?

A

Parent nucleus turns from one nucleus to a daughter nucleus and emits an alpha particle (Helium 4)
Rest energy is conserved

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14
Q

What is beta decay?

A

A neutron turns into a proton and electron emitted
Releases another nucleus with new atom and higher proton number

Process is meant to conserve energy but beta particles which are emitted have less KE ==> Energy not conserved

Neutrinos is the third particle missing

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15
Q

What are anti-particles?

A

Every particle has a corresponding antiparticle with the same mass but opposite charge

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16
Q

Anti particle of an electron?

A

Positron

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17
Q

Antiparticle of a proton?

A

Antiproton

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18
Q

Antiparticle of a neutron and neutrino

A

Antineutron and antineutrino

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19
Q

What is rest energy?

A

The energy a particle with any amount of mass has even while stationary

Measured in MeV

Antiparticle has the same rest energy as their corresponding particle

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20
Q

What is a photon?

A

A quantum of EM radiation

Quanta (discrete packets of energy)

No mass

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21
Q

How to calculate energy of a photon?

A

E = hf

E = energy carried (Joules)
h = Planck’s constant
f = frequency

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22
Q

What is Planck’s constant?

A

6.63 x 10^-34

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23
Q

Wave speed in this case?

A

C = f x wavelength

f = c/wavelength

E=hf or
E=h c/wavlength

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24
Q

Annihilation

A

Conversion of a particle and antiparticle into a pair of gamma ray photons where the rest energy of the particle and antiparticle is converted into the energy of the photons

Photons travel in opposite directions

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24
Q

Total energy when annihilation occurs at rest?

A

2 x rest energy of particle

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25
Q

Total energy when annihilation occurs when moving

A

(rest energy of particle + KE of particle) + (rest energy of antiparticle + KE of antiparticle)

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26
Q

What is pair production?

A

Defined as the process in which a photon is converted into a particle and its own particle in the presence of matter where the energy of the photon is converted to rest energy of particle and anti particle

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27
Q

What is the path in pair production

A

Curved away from each other as in the presence of a magnetic field they have opposite charge

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28
Q

Energy in pair production

A

Energy of photon is converted to rest energy of particle and antiparticle

Excess energy goes to KE

Min energy required for pair production = 2 x rest energy of electron

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29
Q

Four fundamental forces

A

Electromagnetic
Weak nuclear (Nuclear decay)
Strong nuclear (holds the nucleus)
Gravity (ignored in PP)

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30
Q

Gravity

A

Infinite range
Acts on anything with mass
So weak it can be ignored in PP

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31
Q

Electromagnetic

A

Force between all charged particle
Infinite range
Examples -> Annihilation and repulsion of 2 electrons

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32
Q

Strong nuclear force

A

Only acts between hadrons and not leptons

Strongly attractive between 0.5fm and 3fm
Repulsive at less than 0.5 fm
Non existent at great than 3fm

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33
Q

How much is one fm?

A

1 x 10^-15

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34
Q

Weak nuclear force

A

Responsible for beta decay and decay of muons and strange hadrons
Acts on all hadrons and leptons

Conserves charge, baryon and lepton numbers
Charge including neutrino must be weak

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35
Q

Exchange particles

A

Also known as gauge bosons

Known as virtual particles as they are short lived and cant be caught

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36
Q

Definition of exchange particles?

A

Virtual particles which may exist for only a short amount of time and are the mediators of a force by transferring energy and momentum between particles

37
Q

Exchange particle for electromagnetism?

A

Virtual photon

Electron orbits a proton and exchange virtual photons

Photons have no mass and no charge

38
Q

Exchange particle for weak nuclear force?

A

Weak boson

Two types (W+ and W-)
Have the same mass and a relative charge of +1 and -1

Acts on all particles

39
Q

Exchange particle for strong nuclear force

A

Pions

pi +, pi - and pi 0

40
Q

Exchange particle for gravity

A

Only hypothetical gravitons

Never been indirectly or directly observed

41
Q

Use of Feynman diagram

A

Way to visualise how these particle interact

42
Q

How Feynman diagram works

A

Lines at the bottom represent the starting

Those at the end represent the ending particles

Squiggly line drawn crossing is the exchange particle

Angle and direction don’t mean anything

Time flows from bottom to top

43
Q

Electromagnetic interactions

A

No change in particles

Normally between proton and electron

e- + p –> e- + p

Virtual photon emitted by both particle and exchanged

44
Q

Strong nuclear interactions

A

Between a proton and a neutron

p + n –> p + n

Emit and exchange virtual pions

45
Q

Nuclear minus beta decay

A

Neutron turns into a proton

n –> p +e- + antineutrino

W- boson is emitted turning into an electron and anti neutrino

46
Q

Nuclear plus beta decay

A

Proton into a neutron, positron and neutrino

p –> n + e+ + neutrino

W + boson emitted

Electric charge conserved

47
Q

Hadrons

A

Particles that experience the strong nuclear force

48
Q

What are the two classifications of hadrons?

A

Baryons and Mesons

49
Q

What are baryons

A

Heavier hadrons like protons and neutrons

Proton is he only stable baryone

Have a baryon number of +1 (anti have -1)

Contains 3 quarks

50
Q

What are mesons

A

Lighter hadrons like pions and kaons

Comprise of a quark and anti-quark

Lightest hadron and mesons are the pions

pi + and pi - are particle and antiparticle duo

Kaons decay into pions

51
Q

What are leptons?

A

Particles which don’t interact with strong nuclear force

Electrons, muons, electron nuetrino and muon neutrino

Lepton number of +1 and -1

Muons decay into electron and both neutrinos –> same charge as electron

52
Q

What are strange hadrons?

A

Hadrons heavier than the pions - produced by strong nuclear force

K+, K-, K0

Strangeness can be from -3, to +3

K+ has +1 strangeness and K- has -1 strangness

Strangness is conserved in electromagnetic and strong interactions

Not conserved when they decay by weak nuclear

53
Q

What are quarks?

A

Fundamental particles which make up the old fundamental particles

Have charges of + or - 2/3 and + or - 1/3

54
Q

What are the three types of quarks and their relative charge?

A

Up +2/3

Down -1/3

Strange -1/3

55
Q

What is the strangeness of all 3 quarks?

A

Up - 0

Down - 0

Strange - -1

56
Q

What is heavier, strange quarks or up and down quarks?

A

Strange quarks

Explains the difference in mass of strange and normal hadrons

57
Q

Baryon number of quarks and anti-quarks

A

+1/3

-1/3

58
Q

Quark composition of proton and neutron

A

Proton - uud

Neutron - udd

59
Q

Quark composition of antiproton and antineutron

A

Anti-p = anti uu and anti d

Anti-n = anti u and anti dd

60
Q

Quark composition of mesons (Pion and kaon)

A

Pion - u and anti d

Kaon - u and anti s

61
Q

All interactions obey the conservation of?

A

Energy and momentum

62
Q

Interactions by one of the four fundamental forces conserve?

A

Charge
Baryon number
Lepton number

63
Q

Electromagnetic and strong nuclear force always conserve?

A

Strangeness

However, strangeness can decay during interactions mediated by the weak nuclear force

64
Q

What happens to the quarks during beta minus decay

A

Neutron turns into a proton

Down quark changes to an up quark

65
Q

What happens to quarks during beta plus decay?

A

Proton turns into a neutron

Up quark changes to a down quark

66
Q

Photoelectric effect

A

When a metal surface is illuminated by electromagnetic radiation above a certain frequency, the delocalised electrons are liberated from the metal

Electrons are known as photo electrons

67
Q

What is the kinetic energy of these photoelectrons?

A

Can vary from 0 to a maximum

68
Q

What is the threshold frequency of a metal

A

The minimum frequency required of EM radiation for photoelectrons to be emitted from the metal

Energy is needed to overcome electrostatic forces of attraction of ions

69
Q

What is the work function?

A

The minimum energy needed for electrons to escape the metal

70
Q

What happens when EM radiation is below the threshold frequency?

A

No photoelectrons are emitted

Increased intensity does not lead to the emission of photoelectrons

71
Q

What happens to EM radiation above the threshold frequency?

A

Some photoelectrons emitted instantaneously

The intensity has no effect on the kinetic energy

Increasing frequency increases the number of photoelectrons emitted

72
Q

Why is there a threshold frequency?

A

It is a one to one effect where a single electron absorbs a single photon

73
Q

Equation in photoelectric effect?

A

hf = ϕ + Ek(max)

h = Planck’s Constant
f = frequency (Hz)
hf = energy of a photon (J)
ϕ = Work function (J)
E = Maximum kinetic energy of the emitted photoelectrons

74
Q

When the energy of the photon is equal to the work function …

A

The kinetic energy of the emitted photoelectron will be 0

Work function is then h x f

Where f is the threshold frequency

75
Q

Graph of Maximum KE against frequency

A

Ek Max = hf - work function
y = mx + c

Planck’s constant is the gradient

Negative of the work function is the y intercept

Threshold frequency is the x-intercept

75
Q

Excitation

A

The process of an atomic electron absorbing a discrete amount of energy and moving from a lower energy level to a higher energy level

The energy absorbed must be equal to the difference in energy between energy levels

76
Q

When does excitation occur?

A

When a single electron absorbs a single photon or kinetic energy during a collision with a charged particle

77
Q

De-excitation

A

When atomic electron moves from higher energy level to lower energy level, emitting a photon of EM radiation

Excited state is unstable and so de-excitation occurs

78
Q

Ionisation

A

When an electron absorbs sufficient energy to be removed from an atom, creating a positive ion and a free electron

79
Q

Ionisation energy

A

Minimum energy required to remove an electron from its ground state in an atom

= to magnitude of the ground state energy of electron

80
Q

Electron Volt

A

eV = 1.6 x 10^-19 J

MeV = 10^6 x 1.6 x 10^-19J

81
Q

De Broglie’s Hypothesis

A

Light behaved as both a particle and a wave

So any particle can exhibit wave-like properties and behaviour

82
Q

De Broglie’s wavelength

A

wavelength = h/mv

Wavelength is inversely proportion to momentum of the particle

83
Q

Electron diffraction

A

Electrons pass through tin foil and diffract
Produce regions of constructive and destructive interference
Pattern of rings with different intensities
Individual particles still detected

84
Q

Emission line spectra

A

A series of discrete wavelengths of light
Each element has its own distinct spectrum

85
Q

How to figure out frequency of light during de-excitation?

A

Difference in energy between the levels

hf = E2-E1

86
Q

What happens in fluorescent tubes?

A

Electric current flows through - freely moving electrons with KE

Collide with electrons in the atoms of the low pressure gas

Collide and KE is transferred so atomic electrons excite and deexcite and emit photons of UV light

UV photons absorbed by the electrons in the coating o the tube causing them to be excited

Atomic electrons de-excite ad emit photons of visible light

87
Q

How can electrons de-excite?

A

Can de-excite in various waves causing a line spectrum

Can jump energy levels or go one by one

88
Q

Energy of the photons emitted are ..?

A

Low than those o the UV photons absorbed so the frequency are lower and thus similar to visible light

AQA A-Level Physics (9 decks)

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