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IB Physics > atomic, nuclear and particle > Flashcards

atomic, nuclear and particle Flashcards

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1
Q

what does the bohr model show

A

if the angular momentum was quantized the electrons of hydrogen would have discrete energy levels, giving the observed spectral lines.

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2
Q

failures of bohr model

A

Failed to predict the varying intensity or fine detail of hydrogen lines and failed to derive correct energy levels for other atoms

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3
Q

mass-energy equivalence

A

As the mass of an electron and positron can be converted into the energy of gamma radiation, mass and energy must be equivalent

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4
Q

mass of an electron

A

0.5 MeV

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5
Q

1u in MeV

A

1 u = 931.5 MeV

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6
Q

proton mass in kg and u

A
  1. 673 × 10–27kg

1. 007 28u

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7
Q

quantize definition (no need memrise)

A

form into quanta, in particular restrict the number of possible values of (a quantity) or states of (a system) so that certain variables can assume only certain discrete magnitudes.
“light is quantized into packets of energy”

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8
Q

whats a quantum

A

a discrete packet of energy, charge, or any other quantity.

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9
Q

exam electron definition

A

fundamental particle with a charge of -1.6x10^-9 and mass of 9.1x10^-31

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10
Q

antimatter

A

matter made of negative protons (antiprotons) and positive electrons (positrons)

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11
Q

antiparticles

A

for every particle there is an antiparticle which has the same mass but opposite charge

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12
Q

what happens if a particle meets its antiparticle

A

they annihilate each other, turning into high energy photons

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13
Q

amount of energy given out as photons if an electron annihilates a positron

A

1.22 MeV

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14
Q

unit of atomic mass (u)

A

1u is defined as the mass of 1/12 of an atom of a carbon-12 atom

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15
Q

nucleon number(A)

same as atomic mass number

A

number of protons + neutrons

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16
Q

what defines the charge of the nucleus

A

the proton number (Z)

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17
Q

Isotopes

A

nuclides with same proton number but different nucleon numbers

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18
Q

approx energy to remove an electron from an atom

A

~1eV of energy

b/c the energy of an atomic electron is in the region of -1eV

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19
Q

binding energy of a nucleus

A

the energy required to pull the nucleus apart - or amount of energy released when the nucleus is put together

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20
Q

conversion from u (mass unit) to MeV

A

first convert to joules using E = mc^2, then to get to MeV divide by fundamental charge

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21
Q

alpha emission

A

when two protons and two neutrons leave the nucleus as one particle, called an alpha particle (identical to a helium nucleus)

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22
Q

beta emission

A

when a neutron decays to a proton and an electron inside the nucleus
the high energy electron leaves the nucleus as a beta particle

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23
Q

Gamma emission

A

when the nucleus emits a short burst of high-energy electromagnetic radiation

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24
Q

why gamma radiation is different to alpha and beta

A

when alpha and beta particles are emitted the nucleus changes into a different element
when gamma rays are emitted the element does not change

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25
Q

what are beta minus particles and how are they formed

A

They’re electrons formed when a neutron changes to a proton

When this happens an antineutrino is also produced

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26
Q

What’s a beta plus and when is it formed

A

It’s a positron, emitted from the nucleus when a proton changes to a neutron

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27
Q

unit for activity

A

becquerels (emissions per second)

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28
Q

what is tunnelling

A

alphas can get out of the nucleus without going over the potential barrier that holds the nucleons in place

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29
Q

half life

A

the time taken for half the number of unstable nuclei to decay (or activity to halve).

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30
Q

activity (A)

A

the number of decays per second

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31
Q

background radiation

A

radiation of environment, rocks, air, and from the Sun

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32
Q

decay constant

A

the probability of decay in one second. Gives the rate of decay for a given number of nuclei

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33
Q

fusion

A

The joining of small nuclei to make bigger ones with the release of energy.

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34
Q

fission

A

The splitting of large nuclei into smaller ones with the release of energy

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35
Q

baryon

A

made of 3 quarks (e.g. proton uud, neutron ddu)

36
Q

meson

A

made of a quark + antiquark pair (e.g. pi meson)

37
Q

confinement

A

the force required to pull quarks apart is so big that enough energy is transferred to the quarks to produce more quarks so single quarks cannot be observed.

38
Q

pauli exclusion principle

A

particles with spin 1/2 cannot occupy the same energy state.

39
Q

colour charge

A

property of quarks that causes them to experience the strong inter-quark force or ‘colour force’

40
Q

why is antiblue drawn as yellow

A

because yellow and blue = white

41
Q

anti-red

A

cyan

42
Q

anti-green

A

magenta

43
Q

what’s a gluon

A

the exchange particle of the colour force

44
Q

the line spectrum for hydrogen gives evidence for

A

the existence of electron energy levels

45
Q

absorption spectrum

A

when you take white light and pass it through an elemental gas (eg light from the sun through the atmosphere)

46
Q

why use gold foil rutherford

A

gold sheets are only a few atoms deep, so produce results of interactions that could be best related to the interaction between a single alpha and a single nucleus

If the foil was too thick the alpha particles would just be absorbed

47
Q

why vacuum rutherford

A

air would absorb the alpha particles before they hit the foil or before they got to the screen

48
Q

why does the scintillation screen have a phosphorous coating rutherford

A

fluoresces (gives out a photon of visible light) when it is hit by a charged particle. Covering the microscope lens with ZnS allowed the viewer to ‘see’ where the alpha particles hit (or at least count their impacts)

49
Q

weak force mediator

A

mediator: W-bosons (W+, W-, Z+)
particle: quark (mesons)

50
Q

strong force mediator

A

mediator: gluons
particle: quark (baryons)

51
Q

electromagnetic force mediator and particles

A

mediator: photons
particle: leptons

52
Q

exchange particle involved in force between nucleons (nuclear force), and its mass

A

pion, mass 110MeVc^-2

53
Q

nuclear force differences from electric force

A

force much stronger than electric force and has v short range

54
Q

lepton number

A

+1 for leptons and -1 for antileptons

55
Q

2 examples of leptons

A

electrons and neutrinos

56
Q

2 examples of hadrons

A

neutrons and protons (so nucleons)

57
Q

baryon number

A

+1 for baryons and -1 for antibaryons, 0 for mesons and leptons

58
Q

charge number

A

the charge of the particle in multiples of e

59
Q

spin number for baryons and mesons

A

1/2 or 1+1/2 for baryons

0 or 1 for mesons

60
Q

strangeness

A

an extra quantum number that is not conserved in weak interactions

61
Q

what doesn’t the standard model explain?

A

gravity or the existence of the dark matter and energy which is thought to make up 96% of the universe

62
Q

‘external’ products of beta minus decay

A

beta minus particle (electron) and antineutrino

63
Q

what does the wavy line in a feynman diagram represent?

A

an exchange particle

64
Q

neutrino charge

A

zero

65
Q

whats the force between quarks

A

strong force

66
Q

unstable nucleus

A

nucleus that randomly and spontaneously emits particles that carry energy away from the nucleus

67
Q

radioactivity

A

emission of particles and energy from a nucleus

68
Q

emission spectrum definition

A

set of possible wavelengths that can be emitted by a gas

69
Q

decay series

A

set of decays that takes place until a given nucleus ends up as a stable nucleus

70
Q

what does it mean when we say decay is spontaneous

A

cannot affect the rate of decay of a given sample in any way

71
Q

biding energy per nucleon for hydrogen

A

zero because only one particle in the nucleus

72
Q

law of radioactive decay

A

rate of decay is proportional to the number of nuclei that have not yet decayed

73
Q

consequence of law of radioactive decay

A

number of radioactive nuclei decreases exponentially

74
Q

what are the three classes of elementary particles

A

quarks, leptons and exchange particles

75
Q

lepton 3 types

A

electron, muon, tau (and their neutrinos)

76
Q

higgs particle

A

responsible, through its interactions, for the mass of particles of the standard model, in particular the masses of W and Z

77
Q

2 feynman diagram conventions

A
  • time goes left to right

- real particles forward and antiparticles backward

78
Q

all leptons have same charge

A

leptons have charge of -1

79
Q

protons and neutrons held in the nucleus by

A

strong nuclear force

80
Q

nuclide

A

nucleus characterized by specified number of protons and neutrons

81
Q

what causes dark lines in the atomic spectra

A

when photons are absorbed

because they excite atomic electrons into higher energy levels

82
Q

what does the standard model tell us

A

6 quarks, 6 leptons & 4 force carriers are all there is in the universe

83
Q

how to distinguish which boson involved in a weak interaction

A

w+ and w- involved in interactions where there is exchange of charge, z involved when there is no exchange of charge

84
Q

purpose of calculating binding energy per nucleon

A
  • binding energy gives the amount of energy required to remove one nucleon from the nucleus giving an indication of its relative stability
  • per nucleon in order to make comparisons between different nuclei
85
Q

equipment used to measure the change in activity of an isotope over a period of time

A

GM tube

IB Physics (10 decks)

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