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physics paper 2 > nuclear and particle physics > Flashcards

nuclear and particle physics Flashcards

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1
Q

how does the alpha - scattering experiment give evidence of a small dense nucleus

A
  • few alpha particle bounce back
  • this wouldn’t happen if the positive charge in the atom was distributed evenly throughout which suggests they must be hitting a dense positive charge
  • the fact it only happens to a very small number of alpha particles shows the nucleus must be small
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2
Q

what are the main constituents of an atom

A
  • proton
  • neutron
  • electron
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3
Q

how many times bigger is an atom than a nucleus

A

approx 100000 times

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4
Q

what is the letter associated with a proton number

A

Z

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5
Q

what is a nucleon

A

a particle that makes up the nucleus: a proton or a neutron

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6
Q

what letter represents nucleon number

A

A

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7
Q

which is the correct notation

A

AZX

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8
Q

isotope

A

atoms of an element with the same number of protons with a different number of neutrons and therefore a different mass number

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9
Q

strong nuclear force

A

force that holds the nucleus together

  • must overcome the electrostatic force of repulsion between protons but not so much as to cause the nucleus to collapse
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10
Q

describe the range of the strong force

A

repulsive up to 0.5fm
attractive up to 3fm

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11
Q

which has a higher density: an atom or a nucleus

A

nucleus is much more dense than an atom because the atom includes a lot of empty space

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11
Q

equation relating radius of an atom and its nucleon number

A

r = r0A^1/3

r = radius
R0 = constant
A = nucleon number

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12
Q

true or false
every particle has an antiparticle

A

true

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13
Q

give a difference and a similarity between particles and antiparticles

A

similarity - mass
difference - charge

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14
Q

name of antiparticle of an electron

A

positron

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15
Q

hadron

A

type of particle which is affected by the strong nuclear force made of quarks

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16
Q

what are the classes of hadrons

A

baryons - three quarks
mesons - two quarks

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17
Q

two examples of baryons

A

protons and neutrons

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18
Q

four fundamental particles

A
  • strong nuclear
  • weak nuclear
  • electrostatic
  • gravity
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19
Q

which forces are hadrons subject to

A

all four only charge hadrons like protons will be subject to electrostatic forces

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20
Q

leptons

A

fundamental particles which are not subject to strong nuclear force

  • they do still interact via the weak nuclear force
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21
Q

examples of leptons

A
  • electron
  • muon
  • neutrino
  • and their corresponding antiparticles
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22
Q

three types of quark

A
  • up (u)
  • down (d)
  • strange (s)
  • and tehir corresponding antiparticles
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23
Q

quark compesitions of protons and neutrons

A
  • proton (uud)
  • neutron (udd)
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24
Q

true or false; quarks can be found on their own in pairs or in triplets

A

false. quarks are never found on their own

25
Q

what is meant by beta minus decay

A

when a neutron turns into a proton the atom releases an electron and an anti electron neutrino

26
Q

which quark decays in beta minus decay, what does it turn into

A

a down quark turns into an up quark

27
Q

what quantities must be conserved during the decay of particles

A

charge, mass, baryon and lepton numbers

28
Q

what are the defining features of radioactive decay

A

spontaneous and random you can’t predict when an individual nucleus will decay

29
Q

what features of a nucleus might cause it to radioactively decay

A
  • too many or too few neutrons
  • too heavy overall
  • too much energy
30
Q

4 types of radiation

A
  • alpha
  • beta minus
  • beta plus
  • gamma
31
Q

order alpha, gamma, and beta starting with most ionising

A
  • Alpha
  • Beta
  • Gamma
32
Q

alpha particles

A

particle which contains two protons and two neutrons

33
Q

which type of radiation can only be stopped by lead or concrete

A

gamma

34
Q

how far does a beta particle typically penetrate in air

A

50cm - 1m

35
Q

what materials would be needed to investigate whether a radioactive source was releasing alpha, beta or gamma

A
  • alpha = paper
  • beta = 5mm thick aluminium
  • gamma = thick lead sheet
36
Q

a particle with nucleon number, A, and mass number, Z, undergoes alpha decay. what are the nucleon and mass numbers of the resulting particle

A

nucleon number A-4
atomic number Z-2

37
Q

in beta plus decay how Dows the atomic number change

A

decreases

  • proton turns into a neutron and a positron so mass is constant but atomic number decreases
38
Q

activity of a source

A

the number of radioactive decays per second

39
Q

in the equation A = lambdaN what doe each of the letters/ symbols stand for

A

A activity
lambda = decay constant
N = number of radioactive nuclei

40
Q

half life of an isotope

A

average time taken for the activity of a sample or the number of radioactive nuclei to halve

41
Q

what isotope is commonly used to find out how old artefacts are

A

carbon 14

42
Q

what occurs when a particle and antiparticle meet

A

annihilation
- when a particle and its antiparticle meet, they will annihilate each other and releases two gamma rays
- two rays are released in order to conserve momentum
- the mass pf the particles will transform into the energy equivalent

43
Q

pair production

A

gamma ray has enough energy to produce a particle and its antiparticle

44
Q

why does beta plus decay have a very low penetration

A

it will annihilate with matter accost immediately

45
Q

mass defect

A

difference between the total mass of all the nucleons separately compared to the mass of the nucleus

46
Q

why is there a mass defect

A

because energy is released as the nucleons bind together into a nucleus

47
Q

binding energy

A

energy required to separate a nucleus into its constituent parts

48
Q

true or false: a low binding energy per nucleon will mean that an element is more stable

A

false: a low binding energy per nucleon means not much energy would be required to separate the nucleus

49
Q

nuclear fission

A

where a unstable nucleus splits into 2 smaller nuclei. often occurs with the larger nuclei

  • the binding energy per nucleon increases when fission occurs therefore the overall process releases energy
50
Q

what is fusion

A

when two small nuclei fuse together to create a larger nuclei. the new nucleus has a larger binding energy per nucleon than the old nuclei therefore energy is released in the process

51
Q

which precess (fission or fusion) releases the most energy

A

fusion releases a lot more energy per reaction

this is because the change in binding energy is very drastic

52
Q

why is it difficult to make fusion occur on earth

A

there is a large repulsion between the two positively charged nuclei, therefore a lot of energy is required to overcome the repulsion and fuse them together

it is hard to get a material that can withstand the heat and be cost effective

53
Q

how is fission used in nuclear reactors

A
  • rods of uranium - 235 absorb neutrons and become unstable and then split into two daughter nuclei. it also releases 2 or 3 more neutrons. these then go on to be reabsorbed by another uranium-235
54
Q

what is the purpose of a moderator

A

to slow down the neutrons so they travel slow enough to be absorbed by the uranium

they do this through elastic collisions between the moderator and the nucleus

55
Q

why are control rods essential for a nuclear power station

A

they stop the chain reaction from being out of control

they absorb neutrons so that only 1 of the neutrons released in each reaction can go on to be absorbed by another uranium

if not then the nuclear reactor would overheat as too many reactions would happen at once

56
Q

give an example of a material that can be used as a moderator

A

water

57
Q

what is a chain reaction

A

when exactly one neutron from each decay goes on to cause another decay - so the amount of energy released is constant and doesn’t increase ir decrease

58
Q

how is nuclear waste disposed of

A

stored in cooling ponds

it will then be put in sealed steel containers and potentially stored deep underground or underwater

59
Q

give one environmental benefit and risk of nuclear power

A

benefit - no release of greenhouse gas, no contribution to global warming, doesn’t use fossil fuels

risk - leak or escape of material can be catastrophic

physics paper 2 (8 decks)

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