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Physics > P2 topic 6 > Flashcards

P2 topic 6 Flashcards

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1
Q

how is food irradiated with gamma rays?

A

the gamma rays kill off microorganisms on the food even after it has been packaged

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2
Q

how are beta particles used in industry?

A

to detect leaks in underground pipes and to control the thickness of paper during manufacture

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3
Q

how are beta particles used to detect leaks?

A

a beta-particle emitting material, known as a tracer, is fed into the pipe- above ground, a radiation detector detects increased levels of radiation

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4
Q

how are particles used in controlling the thickness of paper?

A

pressure is applied by the rollers to control the thickness of paper- a bets source is placed above the paper and a radiation detector is placed directly below the source and the paper. if the paper is thicker than required, the detector shows an increase in the number of beta particles recorded per unit time- a signal is then sent to the rollers to increase the pressure and reduce the thickness

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5
Q

how is radioactivity used in the home?

A

smoke alarms

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6
Q

how is a current created in smoke alarms?

A

most smoke alarms use a weak alpha source with a long half-life- the alpha particles from the source ionise the air, producing positive ions and electrons. the positive ions are attracted towards the negative terminal of the battery-the electrons travel in the opp direction towards the positive terminal- the ionisation of the air produces a tiny current in the circuit

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7
Q

how do smoke alarms work?

A

when smoke reaches the smoke alarm, it absorbs the alpha particles, causing a drop in the ionisation of the air. the current and the potential difference across the resistor drops. the electronic circuit detects the decrease in pd and triggers the alarm

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8
Q

how are gamma rays used in hospitals?

A

to sterilise equipment and treat and detect cancer

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9
Q

how are gamma rays used to sterilise medical equipment?

A

gamma rays have enough energy to kill bacteria- they are used to sterilise plastic equipment such as syringes and bandages, that cannot be sterilised by heating like metal equipment

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10
Q

how can gamma rays help minimise the risk of infection?

A

sealing syringes in plastic bags then sterilising with gamma rays makes both the package and the contents sterile

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11
Q

how can radioactivity be used to detect cancer?

A

the patient is injected with a small amount of a radioactive tracer, which emits gamma rays- it’s carried around the body in the blood and builds up in the cancerous parts of the body. a gamma camera is used to detect and display the gamma rays that pass through the patient

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12
Q

what is the radioactive tracer used to detect cancer called?

A

technetium-99m

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13
Q

tracer

A

a radioactive material injected into a patient for locating cancer or diagnosing a function of the body

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14
Q

how is radioactivity used to treat cancer?

A

a technique called radiotherapy is used- a gamma source is used to target cancerous cells. by rotating an intense beam of gamma rays, most of the cancerous cells can be killed off with little damage to the healthy cells

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15
Q

what is the gamma source used in treating cancer?

A

cobalt-60

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16
Q

radiotherapy

A

a technique that uses gamma rays to kill cancer cells in the body

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17
Q

what is the weak alpha source usually used in smoke alarms called?

A

americium

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18
Q

why is everything around us slightly radioactive?

A

this is due to background radiation

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19
Q

how can background radiation be detected?

A

it comes from a variety of sources and can be detected using a Geiger counter

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20
Q

Why are rocks naturally radioactive?

A

they contain small traces of radioactive isotopes

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21
Q

which rock is slightly more reactive than other rocks?

A

granite, as it contains higher levels of uranium atoms

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22
Q

what do uranium nuclei naturally decay over time to produce?

A

radon nuclei- radon is a colourless and odourless radioactive gas

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23
Q

how can radon gas get trapped?

A

when structures such as houses are built over granite

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24
Q

what can exposure to radioactive radon lead to?

A

lung cancer

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25
Q

why do different areas of the UK have differing levels of background radiation?

A

due to varying amounts of radioactive sources in that region

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26
Q

background radiation

A

random, low-level radiation that is present everywhere on earth

27
Q

what are the natural sources most background radiation comes from?

A

cosmic rays, rocks and food

28
Q

how do cosmic rays affect the levels of background radiation?

A

they energetic particles such as protons, electrons and neutrinos that come from outer space- they penetrate the Earth’s atmosphere to reach the surface.

29
Q

why does the danger from cosmic rays increase with altitude?

A

there is less atmosphere to stole thx radiation

30
Q

how do rocks contribute to the levels of background radiation?

A

rocks such as granite contain uranium, which decays to produce radioactive radon gas

31
Q

how does food contribute to levels of background radiation?

A

all foods will have minute traces if radioactive nuclei

32
Q

how have humans had an effect on background radiation?

A

nuclear power stations; fallout from previous nuclear weapons tests, explosions and accidents; radiation from equipment/waste from hospitals and industry

33
Q

how much of background radiation is from radon gas?

A

50.1%

34
Q

how much of background radiation is from medical uses?

A

14.3%

35
Q

how much of background radiation is from the ground and buildings?

A

13.5%

36
Q

how much of background radiation is from food and drink?

A

11.6%

37
Q

how much of background radiation is from cosmic rays?

A

10%

38
Q

how much of background radiation is from other sources?

A

0.5%

39
Q

how are gamma rays used in industry?

A

to irradiate food and to check the quality of welding or to detect cracks in metals

40
Q

when is radon gas particularly dangerous?

A

if it remains trapped in the walls of buildings or under floorboards- it rises from ground that contains granite

41
Q

what is an isotope of radon gas?

A

radon-222- it’s a non-reactive noble gas and itself is not a health hazard

42
Q

how are radon-222 nuclei produced?

A

by the decay of radium-226 nuclei

43
Q

how do radium-226 nuclei decay?

A

by alpha emission, with a short half-life of 3.8 days

44
Q

what do the daughter nuclei of radon-222 do?

A

they also emit alpha particles

45
Q

what is believed about radon-222?

A

it may cause cellular damage in the lungs

46
Q

what sort of issues can alpha, beta and gamma radiation cause?

A

alpha, beta and gamma radiations can damage tissue in the human body- if damage is severe, the cells cannot repair themselves. they can also damage DNA, which lead to cancer

47
Q

what do some people believe is a good alternative to fossil fuels?

A

nuclear power

48
Q

what are advantages of coal?

A

cheap, there are enough reserves to last 100 years

49
Q

disadvantages of coal?

A

it causes pollution, costly to control, transportation can be expensive

50
Q

advantages of nuclear power?

A

waste is compact, very little background radiation is produced, only a very low risk of a nuclear accident

51
Q

disadvantages of nuclear power

A

power stations are costly to build and decommission, waste is radioactive for thousands of years, public perception is poor because of the long term dangers posed by accidents

52
Q

low level nuclear waste

A

paper, tools, clothing

53
Q

disposal of low-level waste

A

can be buried in shallow trenches in steel drums

54
Q

disposal of intermediate-level waste

A

buried about 8m underground and shielded by water, concrete or lead

55
Q

disposal of high-level waste

A

can only be stored deep underground or in special tunnels made under mountains

56
Q

what is radioactive decay?

A

random and spontaneous- it cannot be predicted and it isn’t affected by external conditions- some nuclei are very unstable and decay very quickly- others take a long time

57
Q

half life

A

the average time it takes for half of undecayed nuclei in a sample to decay- half life can be micro sounds or thousands of years

58
Q

activity

A

the rate of decay of a source’s nuclei

59
Q

what is activity measured?

A

in becquerel- 100 Bq means that 100 nuclei decay per second and that 100 alpha or beta particles are emitted per second

60
Q

relationship of activity and number of undecayed nuclei

A

activity is directly proportional to the number of undecayed nuclei in a source

61
Q

relationship between activity and half-life of the the isotope

A

activity is inversely proportional to the half-life of the isotope

62
Q

why does activity decrease over time?

A

as radioactive nuclei decay, there are fewer undecayed nuclei

63
Q

exponential decay

A

a graph in which the quantity halves after a given interval of time

64
Q

what precautions should you take when you are using radioactive sources?

A

wear gloves, wash you hands and keep the source pointed away from people

Physics (15 decks)

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