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aqa a level physics > particles and radiation > Flashcards

particles and radiation Flashcards

1
Q

Approximate size of an atom

A

radius of 0.1nm

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2
Q

define ‘isotope’

A

atoms of an element with the same number of protons but different number of neutrons

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3
Q

what is isotopic data? what is its use?

A

The relative amounts of different isotopes of an element found within a substance. Can be used to approximate the age of archaeological finds

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4
Q

How was it deduced that the strong force must exist?

A

The electromagnetic force acts within the nucleus causing repulsion between the similarly charged protons. This is much stronger than the gravitational force acting between all nucleons (due to their mass). If no other forces were present, nucleons would fly apart

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5
Q

Range of the strong force?

A

repulsive at very short range <0.5fm
attractive up to 3fm
negligible afterwards
(very short range)

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6
Q

1fm

A

1 * 10^-15m

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7
Q

What particles experience the electromagnetic force?

A

charged particles

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8
Q

What particles experience the strong nuclear force?

A

hadrons

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9
Q

range of the electromagnetic force

A

infinite

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10
Q

what is nuclear decay

A

unstable nuclei emitting particles to become more stable

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11
Q

describe alpha decay

A

When the nuclei of an atom is too big for the strong nuclear force to keep them stable
they emit an alpha particle (He)

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12
Q

range of an alpha particle

A

short range - few cm in air

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13
Q

How can we observe the range of an alpha particle?

A

Geiger counter - bring it close to a source of alpha radiation and move away. watch count rate drop after a few cm
cloud chamber - alpha particles leave tracks

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14
Q

describe beta minus decay

A

occurs in neutron rich isotopes
the nucleus ejects a beta particle ( fast-moving electron ) and in turn a neutron in the nucleus becomes a proton
an antineutrino is released and carries away some momentum and energy

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15
Q

range of beta particle

A

can travel up to a several metres through air

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16
Q

What led to the hypothesis of neutrinos?

A

to account for conservation of energy
kinetic energies of beta particles varied up to a maximum
had to be neutral so charge was conserved
had to have almost zero mass as it hadn’t been detected

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17
Q

Electromagnetic spectrum

A

radio, micro, IR, visible, UV, x-rays, gamma

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18
Q

frequency

A

number of complete waves passing a point per second

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19
Q

wavelength

A

distance between adjacent crests of wave

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20
Q

the higher the frequency of electromagnetic radiation…

A

the greater its energy

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21
Q

photon energy {}

A

E = hf E = hc/λ

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22
Q

define work function [2]

A

Energy required to remove an electron
Minimum energy required to remove an electron from a (metal) surface

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23
Q

What is meant by an antiparticle [2]

A

Particle with equal (rest) mass/energy
but opposite charge/baryon number/lepton number

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24
Q

how does an antiparticle compare with its corresponding particle?

A

They have the same mass and rest energy
opposite charge

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25
What does the formula E=mc^2 refer to?
pair production energy converted into mass, equal amount of matter and antimatter are produced
26
what are photons?
packets of EM radiation
27
When in an applied magnetic field why do corresponding particles of matter and antimatter curve ?
They have opposite charges hence they curve away from each other
28
How do you calculate the minimum energy needed for pair production?
total rest energy of the particles produced Emin = 2E0
29
1ev in J
* 1.6 * 10^-19
30
1Mev in J
* 1.6 * 10^-13
31
Why are electron-positron pairs more likely to be produced than proton antiproton pairs?
They have a relatively low mass low mass -> low rest energy so less energy required for pair production
32
Mev -> ev
* 10^6
33
what is annihilation
when a particle meets its corresponding antiparticle all mass of the particle and the antiparticles are converted back to energy ( 2 gamma ray photons )
34
How do you calculate the energy of the gamma ray photons produced in annihilation?
energy of the pair = 2E0 produces two gamma ray photons so each gamma ray photon will have energy E0
35
What is an application of annihilation?
PET scanners positron emitting isotope in bloodstream positrons will annihilate with electrons giving off gamma rays which can easily be detected (they also move in opposite directions so can be distinguished)
36
What are the four fundamental forces?
weak strong nuclear force electromagnetic gravitational
37
what is a hadron
a particle that experiences the strong nuclear force ( subject to the strong interaction ) made up of quarks
38
what are the two types of hadrons and what are they made up of
baryons 3 quarks mesons quark antiquark pair
39
What do all baryons eventually decay to and why?
All baryons can be unstable except protons, so they eventually decay to become a proton which is stable
40
what is baryon number?
a quantum number that must be conserved it is the number of baryons protons, neutrons have baryon number +1 antibaryons -1 other particles 0
41
neutron decay
n --> p + e~ + V~ weak interaction
42
what are mesons?
are all unstable have baryon number 0 , quark anti-quark pair they interact with baryons via the strong force
43
what are the lightest mesons
pions exchange particle of the strong nuclear force π±, π0
44
What are the heavier mesons
kaons have a strange quark have a short lifetime and decay into lighter pions K±, K0
45
waffle about cosmic rays detecting mesons
high energy particles from space known as cosmic rays interact with molecules in the atmosphere and produce mesons these leave tracks in a cloud chamber
46
what are leptons
fundamental particles don't feel the strong nuclear force, interact via the weak interaction ( and em and g a bit, em if charged )
47
which leptons are stable and unstable
electrons are stable leptons unstable leptons include muons, tauons, . they are essentially heavy electrons they eventually decay into electrons
48
describe neutrinos
both electrons and muons have their constituent neutrinos, and antineutrinos they have virtually zero mass no charge neutrino - lepton number +1 antineutrino - lepton number -1 lepton electron number and lepton muon number
49
lepton number of a muon antineutrino
electron lepton number 0 muon lepton number -1
50
what are strange particles? how are they created
have a property called strangeness created via the strong interaction in pairs
51
when is strangeness conserved
not in the weak interaction
52
strangeness of K+ K-
+1 -1
53
via which interaction do strange particles decay
weak ( strangeness isn't conserved )
54
what properties need to be conserved in particle interactions?
charge energy momentum baryon/lepton number strangeness ( not in weak )
55
what are quarks
fundamental particles they are the building blocks for hadrons
56
baryon number of the quarks
up 1/3 down 1/3 strange 1/3 everything else 0
57
strange number of the quarks
up 0 down 0 strange -1 everything else 0
58
charge of the quarks
up +2/3 down -1/3 strange -1/3
59
which quarks make up pions
[π0] up, anti-up [π0] down, anti-down [π+1] up, anti-down [π-1] down, anti-up
60
what are the four possible kaons
[K-] anti up strange [K0] antidown strange [K+] up antistrange [K0] down antistrange
61
is it possible to have just 1 quark
quark confinement is not possible pair production occurs instead
62
describe the process of beta minus and plus decay
udd -> uud + e~ + v~ neutron -> proton change of quark character uud -> udd + e+ + v proton -> neutron
63
what can forces also be described as
particle exchange
64
electrostatic repulsion is caused by what?
the exchange of virtual photons transfer energy, momentum they are short lived
65
how is the range of a force determined
the size of the exchange particle heavier exchange particles have shorter range virtual photon has virtual zero mass, infinite range of em w bosons have a mass 100 times as big as a proton's so weak force very short range
66
what is electron capture and how does it differ to electron-proton collision
when a proton rich nuclei captures an electron from the inner shells of an atom and use it to become a neutron electron capture has w+ boson going right -> electron proton collision has w- boson going left <-
67
what is the exchange particle of electromagnetic repulsion
virtual photon

aqa a level physics (10 decks)

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