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BMAT: Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

what is radioactivity?

A

random process where unstable nuclei decay by emitting ionising radiation

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2
Q

what are the three types of ionising radiation?

A
  • alpha
  • beta
  • gamma
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3
Q

properties of alpha particles

A
  • made of 2 protons and 2 neutrons (same as helium nucleus)
  • Mass: 4/ Charge: +2
  • heavy/ big/ slow moving
    HIGH IONISING POWER
    LOW PENETRATING ABILITY - blocked by paper/skin )only travels few cm in air)
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4
Q

properties of beta particles

A
  • essentially an electron so charge of -1
  • small/ fast-moving
    MODERATE IONISING POWER
    MODERATE PENETRATING ABILITY - blocked by thin aluminium (travels 20-30cm in air)
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5
Q

properties of gamma rays

A
  • EM waves so have no mass/charge
    LOW IONISING POWER
    HIGH PENETRATING ABILITY - blocked by thin lead/ thick concrete
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6
Q

what is activity?

A

number of nuclei that decay per second

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7
Q

what is count rate?

A

number of radioactive emissions detected per unit of time

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8
Q

what happens during alpha decay?

A

loses 2 protons/ 2 neutrons

so atomic number decreases by 2 and mass number decreases by 4

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9
Q

what happens during beta decay?

A

neutron splits into proton and electron

so atomic number increases by 1 and mass number stays the same

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10
Q

why are alpha and beta particles deflected in opposite directions by magnetic/electric field?

A

because they have opposite charges

- alpha feel a greater force but are deflected less because of greater mass

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11
Q

what is radiation dose depend on and what is it measured in?

A

location and occupation

measured in sieverts (Sv)/ millisieverts (mSv)

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12
Q

give examples where exposed to high radiation doses

A
  • radiography - stand behind lead screen/ wear lead aprons
  • uranium miners/ nuclear industry - protective clothing
  • underground rocks - release radon gas - mining in general is risk to health
  • high altitudes - commercial pilots exposure to cosmic rays from sun
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13
Q

what contributes to background radiation?

A
  • natural sources
  • radon gas
  • human acitivity: nuclear industry/ industrial waste
  • cosmic rays
  • medical X-rays
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14
Q

what is half-life?

A

average time for radioactive nuclei in a radioactive isotope sample to halve

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15
Q

unit of radioactivity

A

becquerels (Bq)

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16
Q

how is alpha radiation used for smoke alarms?

A

weak source of alpha radiation placed between two electrodes

  • source causes ionisation so current flows through alarm
  • if smoke, it absorbs radiation. cutting current and sounding alarm
17
Q

how is beta radiation used for thickness control?

A

connected to control unit - fluctuating amounts of radiation adjusts rollers to give correct thickness- source has long half-life so doesnt decay too quickly

18
Q

what is gamma radiation used for?

A
  • sterilising equipment

- cancer treatment - radiotherapy

19
Q

which type of radiation is most dangerous outside body?

A

beta/gamma - penetrate through get to delicate organs

20
Q

which type of radiation is most dangerous inside body?

A

alpha - damages in localised area

21
Q

what is nuclear fission?

A

splitting of atomic nuclei by absorbing slow moving neutron and also releases 2 more neutrons

22
Q

how is nuclear fission used for generating electricity>

A

releases lots of energy heats water turns to steam which spins steam turbines and produces electricity

23
Q

how are chain reactions regulated?

A

control rods absorb some of the neutrons to slow down reaction

24
Q

what fuel is usually used for nuclear fission?

A

uranium- 235 or plutonium-239

25
Q

what is the fission equation for uranium-235?

A

1/0 n + 235/92 U –> 236/92 U

–> 144/56 Ba + 90/36 Kr + 2 x 1/0 n

26
Q

what is nuclear fusion?

A

joining smaller nuclei together to form larger one e.g. hydrogen isotopes

27
Q

equation for fusion of hydrogen isotopes

A

1/1 H + 2/1 H –> 3/2 He

28
Q

why is nuclear fusion signficant as energy source>

A

releases lots of energy but needs high temp/pressure which is hard to control
- used in hydrogen bombs

BMAT: Physics (6 decks)

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