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physics > radioactivity > Flashcards

radioactivity Flashcards

1
Q

what is the mass number also known as?

A

the nucleon number

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2
Q

what is the mass number?

A

n. of protons & neutrons

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3
Q

what is the atomic number also known as?

A

the proton number

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4
Q

what is the atomic number?

A

n. of protons

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5
Q

what are isotopes?

A

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

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6
Q

why is a radioisotope unstable?

A

it has too many neutrons- decays and emits radiation randomly

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7
Q

radioisotopes randomly emit alpha or beta particles or gamma radiation to form what?

A

a new atom with a different number of protons

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8
Q

where is radiation emitted from?

A

the nucleus of an unstable atom

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9
Q

radiation happens…

A

randomly

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10
Q

radiation from a nucleus can take what 3 forms?

A
  • alpha
  • beta
  • gamma
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11
Q

what is an alpha particle?

A
  • a helium nucleus
  • 2 protons, 2 neutrons
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12
Q

what charge does an alpha particle have?

A

+2 charge

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13
Q

are alpha particles fast or slow?

A

quite slow

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14
Q

are alpha particles big or small?

A

massive (relatively)

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15
Q

what does radium become when it decays?

A

radon

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16
Q

what is a beta particle?

A
  • a very fast electron emitted from the nucleus
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17
Q

what is the charge on a beta particle?

A

-1 charge

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18
Q

are beta particles fast or slow?

A

fast

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19
Q

do beta particles have a big or small mass?

A

very small mass

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20
Q

what is a gamma wave?

A
  • an electromagnetic wave- very short wavelength, very high frequency
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21
Q

do gamma waves have a charge?

A

no charge

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22
Q

are gamma waves slow or fast?

A

extremely fast- speed of light (3 x10 to the power of 8)

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22
Q

what is the mass of an alpha particle?

A

4u- heavy (massive)

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23
Q

what is the mass of a beta particle?

A
  • 1/1850
  • very small
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24
Q

what is the mass of a gamma wave?

A

0

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25
Q

what is the penetrating power like for alpha particles?

A
  • low
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26
Q

why is penetrating power low for alpha particles?

A
  • cannot get through materials easily
  • stopped by 5cm of air & by thin aluminium
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27
Q

what is the penetrating power like for beta particles?

A

mid power

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28
Q

why do beta particles have medium penetrating power?

A

stopped by mm of aluminium

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29
Q

what is the penetrating power like for gamma waves?

A

high

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30
Q

why is the penetrating power high for gamma waves?

A
  • stopped by thick lead or concrete
  • can travel long distances in air
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31
Q

what is ionisation?

A

the process of adding or removing electrons from atoms

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32
Q

do alpha and beta have lots of kinetic energy?

A

yes- they are moving fast

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33
Q

what is half life?

A

the time taken for half the radioactive nuclei to decay

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34
Q

why do we measure half life?

A
  • the decaying process is random
  • we can’t measure the whole life of a radioactive material
  • so we have to measure half life
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35
Q

how is the beta electron formed?

A

when a neutron in the nucleus splits into a proton and an electron

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36
Q

the beta electron (negative) is always…

A

0
-1

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37
Q

how is a positive ion left behind?

A

the radiation provides energy to allow outer shell electron to escape the pull of the nucleus- leaving a positive ion behind

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37
Q

the beta proton is always…

A

0
+1

38
Q

what is activity?

A

number of decays per second in Becquerels (Bq)

38
Q

why is alpha less penetrating than beta & gamma?

A
  • alpha- large mass & a 2+ charge
  • large mass: more chance to interact with atoms in material it travels through- more chance of ionisation- transfer of energy
  • 2+ charge: attracts negative charge (electrons)- helping ionisation
39
Q

beta has a negligible mass & a 1- charge- what does this mean in terms of ionisation?

A
  • negligible mass: less chance of interaction with atoms-less ionisation
  • 1- charge: repel negative electrons- dont help ionisation
40
Q

is gamma a strong or weak ioniser?

A

very weak ioniser

41
Q

which is the most dangerous inside the body?

A

alpha- weak penetrator- cannot get out- has strong ionising power- loses all energy inside the body

42
Q

which is the least dangerous inside the body? -

A

gamma is least dangerous- has weak ionising power

43
Q

which is the most dangerous outside the body?

A

gamma- strong penetrator

44
Q

what does penetrate mean?

A

the ability of each radiation to pass through material

45
Q

what does the more material the radiation can pass through mean?

A
  • the greater the penetration power
  • the more dangerous they are
46
Q

what 3 factors do we need to consider when choosing which source of radiation we want to use?

A
  • type of radiation needed
  • penetrating power
  • half life
47
Q

what type of radiation is used for sterilising medical equipment?

A

gamma

48
Q

what type of half life does gamma radiation have when sterilising medical equipment?

A

long

49
Q

what type of radiation is used when killing cancer cells?

A

gamma radiation

50
Q

what type of half life does gamma radiation have when killing cancer cells?

A

short half life

51
Q

what type of radiation is used when gauging thickness in paper or sheet metal factories?

A

beta

52
Q

what type of radiation is used for tracers- to find water leaks in underground pipes?

A

gamma

53
Q

what type of half life is used for gamma radiation for tracers to find water leaks in underground pipes?

A

short

54
Q

what type of radiation is used for medical tracers in the body?

A

gamma

55
Q

what type of half life does gamma radiation have for medical tracers in the body?

A

short half life

56
Q

what type of radiation is used for nuclear fission & fusion?

A

alpha

57
Q

what type of half life is used for alpha radiation for nuclear fission & fusion?

A

long

58
Q

what is nuclear fission?

A

splitting of a heavy unstable nucleus (U235) to release energy

59
Q

what is nuclear fusion?

A

the joining of 2 light nuclei to release energy

60
Q

what does adding a neutron do to a molecule?

A

makes it more unstable

61
Q

what happens in terms of energy when nuclear fission happens?

A

lots of energy is released from the nucleus- from the nuclear store

62
Q

what does nuclear fission involve?

A

a nucleus splitting into two large fragments

63
Q

what are the products of nuclear fission called?

A

daughter nuclei

64
Q

what do most isotopes need to split?

A

most need to be induced to split by absorbing another particle- usually a neutron

65
Q

what are the isotopes most used in nuclear reactors?

A

uranium 235 and plutonium 239

66
Q

the fission of 235U- fast neutron?

A

fast neutrons pass through the uranium nucleus, without causing it to split

67
Q

the fission of 235U- slow neutron?

A

slow neutrons are absorbed by the 235U nucleus, becoming an unstable 236U which then splits into 2 smaller nuclei and 3 fast neutrons

68
Q

why do we need slow neutrons in nuclear fission?

A

we need slow neutrons so they can be absorbed

69
Q

uncontrolled chain reaction- what happens if the mass of uranium is too large?

A
  • the rate of the fission reaction increases very rapidly
  • the temperature rises by thousands of degrees in a fraction of a second and a nuclear explosion results
70
Q

controlled chain reaction- what happens if the mass of uranium is a little lower?

A
  • if the mass is a little lower and a material is used to absorb excess neutrons, then the rate of fission can be controlled
  • this means the uranium can be kept hot (few hundred degrees) for years
71
Q

what type of chain reaction do we have in nuclear power stations?

A

controlled chain reaction

72
Q

what does an uncontrolled chain reaction result in?

A

a nuclear bomb

73
Q

what is needed to make use of the energy from nuclear fission?

A
  • fuel rods
  • control rods
  • a moderator
  • some means of transferring the heat generated into electricity
  • shielding
74
Q

what are the fuel rods enriched with?

A

U-235

75
Q

what are the control rods made out of?

A

boron

76
Q

what do the control rods do?

A

absorb neutrons

77
Q

what does the moderator do?

A

slows down fast neutrons so they can keep the reaction going

78
Q

what does shielding do?

A

protects the environment and us from harmful radiation

79
Q

what is the shielding made out of?

A

thick concrete

80
Q

what does the fuel rods being lowered and raised mean?

A
  • lowered- fuel rods cool down
  • raised- fuel rods heat up
81
Q

the energy released goes into what store?

A

nuclear store- KE- thermal- KE- electricity

82
Q

how does fission happen?

A

fire a neutron at U235 to split it

83
Q

how does fusion happen?

A

H&H join to make a heavier nucleus

84
Q

what conditions does fission require?

A

need to be moderated to a slower speed

85
Q

what conditions do fusion require?

A

high temperatures and pressure to overcome repulsive forces between 2 positive hydrogens

86
Q

what particles does fission produce?

A
  • 2 daughter nuclei and a small number of radioactive neutrons
87
Q

what particles does fusion produce?

A

helium nucleus

88
Q

why is energy released in fission?

A

the kinetic energy of all the fission products

89
Q

why is energy released in fusion?

A

released energy comes from a loss of mass of the smaller nuclei

90
Q

where does fission happen?

A

in nuclear reactors used to generate electricity

91
Q

where does fusion happen?

A

in the stars- it is a star’s source of energy

92
Q

fission only happens if the neutron colliding with U235 is….

A

slow

93
Q

fusion does not happen at…

A

low temperatures & pressures

94
Q

key sources of background radiation?

A
  • cosmic rays from space
  • the ground- particular rocks
  • gases- e.g. radon gas
  • food- organic food has carbon 14

physics (47 decks)

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