P2 topic 6

Question 1

how is food irradiated with gamma rays?

Answer 1

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

Question 2

how are beta particles used in industry?

Answer 2

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

Question 3

how are beta particles used to detect leaks?

Answer 3

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

Question 4

how are particles used in controlling the thickness of paper?

Answer 4

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

Question 5

how is radioactivity used in the home?

Answer 5

smoke alarms

Question 6

how is a current created in smoke alarms?

Answer 6

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

Question 7

how do smoke alarms work?

Answer 7

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

Question 8

how are gamma rays used in hospitals?

Answer 8

to sterilise equipment and treat and detect cancer

Question 9

how are gamma rays used to sterilise medical equipment?

Answer 9

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

Question 10

how can gamma rays help minimise the risk of infection?

Answer 10

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

Question 11

how can radioactivity be used to detect cancer?

Answer 11

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

Question 12

what is the radioactive tracer used to detect cancer called?

Answer 12

technetium-99m

Question 13

tracer

Answer 13

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

Question 14

how is radioactivity used to treat cancer?

Answer 14

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

Question 15

what is the gamma source used in treating cancer?

Answer 15

cobalt-60

Question 16

radiotherapy

Answer 16

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

Question 17

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

Answer 17

americium

Question 18

why is everything around us slightly radioactive?

Answer 18

this is due to background radiation

Question 19

how can background radiation be detected?

Answer 19

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

Question 20

Why are rocks naturally radioactive?

Answer 20

they contain small traces of radioactive isotopes

Question 21

which rock is slightly more reactive than other rocks?

Answer 21

granite, as it contains higher levels of uranium atoms

Question 22

what do uranium nuclei naturally decay over time to produce?

Answer 22

radon nuclei- radon is a colourless and odourless radioactive gas

Question 23

how can radon gas get trapped?

Answer 23

when structures such as houses are built over granite

Question 24

what can exposure to radioactive radon lead to?

Answer 24

lung cancer

Question 25

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

Answer 25

due to varying amounts of radioactive sources in that region

Question 26

background radiation

Answer 26

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

Question 27

what are the natural sources most background radiation comes from?

Answer 27

cosmic rays, rocks and food

Question 28

how do cosmic rays affect the levels of background radiation?

Answer 28

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

Question 29

why does the danger from cosmic rays increase with altitude?

Answer 29

there is less atmosphere to stole thx radiation

Question 30

how do rocks contribute to the levels of background radiation?

Answer 30

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

Question 31

how does food contribute to levels of background radiation?

Answer 31

all foods will have minute traces if radioactive nuclei

Question 32

how have humans had an effect on background radiation?

Answer 32

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

Question 33

how much of background radiation is from radon gas?

Answer 33

50.1%

Question 34

how much of background radiation is from medical uses?

Answer 34

14.3%

Question 35

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

Answer 35

13.5%

Question 36

how much of background radiation is from food and drink?

Answer 36

11.6%

Question 37

how much of background radiation is from cosmic rays?

Answer 37

10%

Question 38

how much of background radiation is from other sources?

Answer 38

0.5%

Question 39

how are gamma rays used in industry?

Answer 39

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

Question 40

when is radon gas particularly dangerous?

Answer 40

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

Question 41

what is an isotope of radon gas?

Answer 41

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

Question 42

how are radon-222 nuclei produced?

Answer 42

by the decay of radium-226 nuclei

Question 43

how do radium-226 nuclei decay?

Answer 43

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

Question 44

what do the daughter nuclei of radon-222 do?

Answer 44

they also emit alpha particles

Question 45

what is believed about radon-222?

Answer 45

it may cause cellular damage in the lungs

Question 46

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

Answer 46

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

Question 47

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

Answer 47

nuclear power

Question 48

what are advantages of coal?

Answer 48

cheap, there are enough reserves to last 100 years

Question 49

disadvantages of coal?

Answer 49

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

Question 50

advantages of nuclear power?

Answer 50

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

Question 51

disadvantages of nuclear power

Answer 51

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

Question 52

low level nuclear waste

Answer 52

paper, tools, clothing

Question 53

disposal of low-level waste

Answer 53

can be buried in shallow trenches in steel drums

Question 54

disposal of intermediate-level waste

Answer 54

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

Question 55

disposal of high-level waste

Answer 55

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

Question 56

what is radioactive decay?

Answer 56

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

Question 57

half life

Answer 57

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

Question 58

activity

Answer 58

the rate of decay of a source's nuclei

Question 59

what is activity measured?

Answer 59

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

Question 60

relationship of activity and number of undecayed nuclei

Answer 60

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

Question 61

relationship between activity and half-life of the the isotope

Answer 61

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

Question 62

why does activity decrease over time?

Answer 62

as radioactive nuclei decay, there are fewer undecayed nuclei

Question 63

exponential decay

Answer 63

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

Question 64

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

Answer 64

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