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physics > radioactivity ✓ > Flashcards

radioactivity ✓ Flashcards

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1
Q

what is the activity of a source ?

A

how many emissions happen per second

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2
Q

what do you measure activity in ?

A

Becquerels Bq

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3
Q

what is the basic structure of an atom ?

A

has protons and neutrons in the nucleus and then electrons on the outer shell

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4
Q

what is the difference between an atom and an ion ?

A
  • ion is a particle or collection of particles with a net positive or negative charge
  • stable atom contains the same number of electrons as protons and no net charge
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5
Q

what is the proton number ?

A

the number of protons in the nucleus

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6
Q

what is the nucleon number ?

A

the total number of protons and neutrons in the nucleus

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7
Q

how do you find the number of neutrons ?

A

minus the proton number from the nucleon number

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8
Q

14
C
6

what is the proton number in carbon-14 ?

A

6

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9
Q

14
C
6

what is the nucleon number in carbon-14 ?

A

14

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10
Q

14
C
6

what is the neutron number in carbon-14 ?

A

8

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11
Q

some isotopes are 1………. and some are 2………. and so will 3…………. (fill in blanks)

A
  1. stable
  2. unstable
  3. radioactively decay
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12
Q

what are some examples of stable carbon isotopes ?

A

Carbon-12 (C-12) and Carbon-13 (C-13)

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13
Q

what is an example of an unstable carbon isotope ?

A

Carbon-14 (C-14)

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14
Q

why can’t you predict when radioactive decay will happen ?

A

because it is spontaneous and random

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15
Q

what are alpha, beta and gamma ?

A

ionising radiation

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16
Q

what are alpha, beta and gamma emitted from ?

A

unstable nuclei

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17
Q

describe alpha particles in 7 statements

  • what is the symbol ?
  • what is it ?
  • what is its relative mass ?
  • what is its electrical charge ?
  • how strongly ionising is it ?
  • how penetrating is it ?
  • how fast can it travel ?
A
  • α
  • 2 protons and 2 neutrons
  • 4
  • +2
  • very
  • paper of 5cm air
  • relatively slow
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18
Q

describe beta particles in 7 statements

  • what is the symbol ?
  • what is it ?
  • what is its relative mass ?
  • what is its electrical charge ?
  • how strongly ionising is it ?
  • how penetrating is it ?
  • how fast can it travel ?
A
  • β
  • emitted electron
  • 1/1836
  • -1
  • moderately
  • 5mm aluminium
  • very fast
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19
Q

describe gamma particles in 7 statements

  • what is the symbol ?
  • what is it ?
  • what is its relative mass ?
  • what is its electrical charge ?
  • how strongly ionising is it ?
  • how penetrating is it ?
  • how fast can it travel ?
A
  • γ
  • electromagnetic wave
  • 0
  • 0
  • not very
  • 5cm lead or 5m concrete
  • speed of light
20
Q

what two ways can ionising radiation be detected ?

A

photographic film

Geiger-Müller detector

21
Q

what is the use of radioactivity for medical uses ?

A
  • medical instruments are sterilised
  • radiotherapy
  • medical tracers
22
Q

how does radiotherapy work ?

A
  • beam of gamma is directed at the cancerous tumour in patient
  • ionises cancerous cells and kills them
  • source is rotated so the beam always passes through the tumour
23
Q

what are the dangers of radiotherapy ?

A

risk of secondary cancer as healthy cells are also ionised

24
Q

how does a medical tracer work ?

A
  • patient is injected with gamma source
  • progress of tracer is then tracked by doctor s
  • as it passes through the body it indicates problems
25
Q

how does a non-medical tracer work ?

A
  • add radioactive tracer to the water
  • where leak is located large amounts of the water collect
  • this means large amounts of radiation will be detected above the leak
  • allows to dig up and fix pipe in correct place
26
Q

why gamma used in the medical and non-medical processes ?

A

because it moves very fast and it very penetrating

27
Q

what is the effect of alpha emissions on a nucleus ?

A
  • alpha radiation reduces the ratio of protons to neutrons in parent nucleus
  • making it a more stable configuration
28
Q

what is the effect of beta emissions on a nucleus ?

A

when a nucleus emits a beta particle, these changes happen:
the mass number stays the same
the atomic number increases by 1
the nuclear charge increases by 1

29
Q

what is the effect of gamma emissions on a nucleus ?

A

do not alter proton or neutron number instead has the effect of moving the nucleus from a higher to a lower energy state

30
Q

what are the main sources of background radiation ?

A
  • random gas from the ground 40%
  • human body and food 15%
  • cosmic rays 12%
  • rocks 15%
  • artificial sources 18%: - medical
    - nuclear power and weapons test
    - other sources
31
Q

how do measurements using the Geiger Müller detector account for background radiation ?

A
  • measure with no radioactive sources in the room start a stopwatch and GM tube at the same time
  • after 60 seconds, stop the GM tube and counter and record the number of counts in 60 seconds
  • calculate background activity in the room
  • repeat the process a number of times and find the average background activity
32
Q

what happens to the activity of a radioactive source over time ?

A

it decreases

33
Q

how does half life work ?

A
  • at start all the nuclei are unstable
  • after one half life half of the unstable nuclei have decayed and are now stable
  • after the next half life half of the remaining nuclei are unstable and will decay
  • this process continues
34
Q

in what atoms is half life different for ?

A

half life is different for different isotopes

35
Q

how long does it take for half life to occur ?

A

ranges from billions of years to millionths of a second

36
Q

how is half life used to infer age of archaeological specimens ?

A
  • some elements decay into another element through chains of decays
  • we can look at rocks of the element and examine how much has decayed into the other element
  • this helps us work out how old the element or rock is
37
Q

describe the fission of Uranium-235

A
  • U-235 absorbs a slow moving electron
  • fission of U-236 creates two daughter nuclei and a small number of neutrons
  • the daughter nuclei and neutrons have a lot of kinetic energy (temperature is a measure of kinetic energy)
  • the neutrons could go on and strike another U-235 causing further fission reactions
  • this creates a chain reaction
38
Q

what is the role of the control rods in the fission of U-235 ?

A
  • these can absorb neutrons so that for every 2 or 3 neutrons that are released from a fission reaction, only 1 goes on to produce further fission
  • they can also be used to stop the reaction.
39
Q

what is the role of the moderator in the fission of U-235 ?

A

moderates the speed of the neutrons

40
Q

how can nuclear fission be used in power stations to generate electricity ?

A
  • heat from fission reaction heats water above
  • boiled water (steam) drives a turbine
  • turbine turns generator
  • generator generates electricity using electromagnetic induction
  • distributes electricity
  • water is recycled
41
Q

what are some problems associated with disposal of nuclear waste ?

A
  • it has a high radioactivity

- generates heat so has to be constantly cooled

42
Q

how is fusion different to fission ?

A

fission: breaking large nuclei into smaller nuclei
fusion: joining small nuclei to make big nuclei

43
Q

how do you describe fusion ?

A

fusing smaller nuclei into larger nuclei and overall there is a loss of mass and an associated release of energy

44
Q

what is fusion in the stars ?

A

it is the energy source of the stars

45
Q

how do you minimise risks from nuclear wastes ?

A
  • vitrification: bind the waste within glass which is poured into containers and solidifies
  • bury waste away from fresh water sites: to avoid contamination
  • keep waste in lead lined containers: can’t penetrate lead
  • handle waste remotely: use robots
46
Q

how does the fusion of hydrogen to make helium work ?

A
  • Hydrogen (proton number 1) is fuses together to make Helium (proton number 2)
  • when fusion happens there is an overall loss in mass resulting in a release of energy
  • fusion can only happen at high temperature and pressure
  • this is because in order to fuse two protons together you have to overcome the electrostatic repulsion between them

physics (8 decks)

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