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Flashcards in Radioactivity Deck (98):
1

What are the three types of ionising radiation? Where are they emitted from?

alpha particle

beta particle

gamma rays

they are emitted from unstable nuclei

2

The ionising radiation are emitted for ... reasons. What are the reasons?

The ionising radiation are emitted for different reasons:

in a metastable state

the nucleus is too large

has too many protons

has too many neutrons

3

What is radiation?

the spontaneos and random emission of energy from unstable nuclei

4

Can you predict when a nucleus will emit radiation exactly?

No, but you can estimate on average

5

Can you do anything to the physical properties to affect the rate of radiation?

no

6

Why are aplha, beta and gamma radiation ionising?

because they ionise matter as they pass through it (knock electrons out of orbit)

ionisng matter requires work to be done by the radiation so they slow down

7

The more alpha, beta and gamma radiation ionise, the ... their penetration through the matieral

The more alpha, beta and gamma radiation ionise, the shorter their penetration through the matieral

8

What are Alpha Particles made up of? What is this identical to?

2 protons and 2 neutrons (identical to a Helium nucleus)

9

What is a Beta Particle?

it is an electron

10

What are Gamma rays?

high frequency, short wavelength electromagnetic rays

11

What is the mass of an Alpha Particle?

2 protons + 2 neutrons

12

What is the mass of a Beta Particle?

the mass of an electron

13

What is the charge of an Alpha Particle?

+ 2 electrons

14

What is the charge of a Beta Particle?

-1 electron

15

What is the charge of a Gamma Ray?

no charge

16

As the heaviness of the ionising radiation increases, the ... ...

As the heaviness of the ionising radiation increases, the speed decreases 

17

What is the order of heaviness (most to least) and of ionising radiation? Then what is the order of speed (most to least)

Heavy:

alpha

beta

gamma

Speed:

gamma

beta

alpha

18

Are gamma rays ionising?

not very

19

What is the speed of gamma rays?

speed of light

20

The more ionising the ionising radiation the ... able to ...

The more ionising the ionising radiation the less able to penetrate in materials

21

What is the order of ionising of the ionising radiation (most to least)? Then, what is the order of penetration in materials (most to least)?

Ionising:

alpha

beta

gamma

Penetration:

gamma

beta

alpha

22

What can Alpha Particles penetrate?

it cannot even penetrate paper

23

What can Beta Particles penetrate?

paper

weak Beta Particles can pentrate aluminum foil

24

What can Gamma Rays penetrate?

paper

aluminium

their energy decreases as they travel through concrete or dense materials like lead

25

What are Alpha Particles absorbed by?

skin

paper

10 cm in air

26

What are Beta Particles absorbed by?

a few mm of aluminium

27

What are Alpha Particles emitted from?

the nucleus of a large, heavy, unstable isotope

28

What are gamma rays absorbed by?

thick lead

very thick concrete

29

What are Beta Rays emitted from?

the nucleus when there are too many neutrons for it to be stable

a neutron decyas into a proton and emits a Beta particle

30

What happens if there are too many protons in the nucleus for it to be stable?

a positive electron (positron) is emitted - this is rare

31

What are Gamma Rays emitted from?

a nucleus in a high energy state - sometimes called a metastable

32

How can ionising radiation be detected?

ionising radiations can be detected using a photographic film or a Geiger-Muller detector

33

What is background radiation?

background radiation is low-level ionisng radiation that is around us all the time due to a mixture of natural and man-made sources

34

What are four natural sources of background radiation?

Cosmic rays radiation that reaches the Earth from spac

Rocks and soil - some rocks are radioactive and give off radioactive radon gas

The atmosphere - C14 in the air

Living things - plants absorb radioactive materials from the soil and these pass up the food chain

35

What are five man-made sources of background radiation?

Nuclear power stations - move dangerous when they explode e.g. Chernobyl

X-rays

Nuclear medicine

Nuclear bombing

Nuclear power plants

36

How do you record background radiation?

connect a Geiger-Muller tube to a Geiger-MUller counter

ensure that there is no other sources of radiation in a room

leave them for 10 minutes

the counted number is the background radiation

37

Why do we record background radiation before taking any activity measurements?

we need to take away background radiation when measuring anything else so it does not interfere with our results and make them inaccurate

38

What is the atomic number>

also called the proton number

number of protons which also equals the number of electrons

atomic number = number of protons = number of electrons

39

What is the mass number?

also known as the nucleon number

the number of protons + number of neutrons

40

What is an isotope?

atoms of an element with the same number of same protons number but different number of neutrons (so a different mass number)

41

What is carbon-14

an unstable isotope of carbon

it is radioactive - the nucleus is unstable so it decyas and emits radiation

42

What does nuclear radiation cause? How?

nuclear radiation causes ionisation by bashing into atoms and knocking electrons off them. Atoms (with no overall charge) are turned into ions (which are charge) - ionisation

this requires the radiation to do work and therefore it transfers some of its energy to the ion pair

43

What do electric and magnetic fields do to alpha particles?

because they're electrically charged (with a positive charge), alpha particles are deflected (their direction changes) by electric and magnetic fields

44

What does emitting an alpha particle do to the atomic number and the mass number?

emmitting an alpha particle decreases the atomic number of the nucleus by 2 and the mass number by 4

45

What do electric and magnetic fields do to beta particles?

Because they're charged (negatively), beta particles are deflected by an electric and magnetic fields

46

What does emmiting a beta particle do to the atomic number and the mass number?

emmiting a beta particle increases the atomic number by 1 but the mass number stays the same

47

What does emmiting gamma ray radiation do to the atomic number and the mass number

emmiting gamma ray radiation has no effect on the atomic number or the mass number

48

What happens to the activity of a radioactive source over a period of time?

the activity of a radioactive source decreases over a period of time

49

What happens each time a decay happens?

each time a decay happens and an alpha particle, beta particle or gamma ray is given out, it means one more radioactive nucleus has disappeared - hence why radioactivity decreases over time

50

The older a sample becomes, the more/less radiation it will emit

The older a sample becomes, the less​ radiation it will emit

51

Does radioactivity ever reach zero?

no - this is why we have to use the idea of half-life to measure how quickly the activity drops off

52

What is radioactivity measure in?

becquerels (Bq)

53

What does 1 Bq equal?

1 Bq = 1 decay per second

54

What is the defintion of half-life?

the time taken for the activity of a radioactive isotope to halve

or the time taken for the amount of radioactive isotope to halve

55

Is the half-life always the same?

no - the half-life is different for different radioactive isotopes

56

What does a short half-life mean?

a short half-life means the activity falls quickly because lots of nuclei decay quickly

57

What does a long half-life mean?

a long half-life means the activity falls more slowly because most of the nuclei don't deacy for a long time - they just sit there, basically unstable, but kind of biding their time

58

The activity of a radioisoptope is 640 Bq. Two hours later it has falled to 40 Bq. find the half-life of the sample

Initial count: 640

After one half-life: 640 ÷ 2 = 320

After two half-lives: 320 ÷ 2 = 160

After three half-lives: 160 ÷ 2 = 80

After four half-lives: 80 ÷ 2 = 40

There are four half-lives for the activity tot fall from 640 to 40

Two hours = four half-lives

1 hour = two half-lives

30 mins = one half life

the half-life = 30 minutes

59

How does a thickness control machine work?

The machine can be used to produce thin sheets of paper, aluminium and lead

The thickness is controlled by the amount of radiation received by the detector that has passed through the material

The detector is attached to the pressure control, which can move two rollers closer together or further apart, depending on the amount of radiation received by the detector

60

Describe what would happen to the thickness control equipment if the material produced was too thick

if the material is too thick, less radiation arrives at the detector

the detector sends a signal to the pressure control that the level of radiation is too low

the pressure control makes the gap between the rollers smaller

the smaller gap makes the material thinner until the amount of radiation at the detector increases to its normal level

61

Describe what would happen to the thickness control equipment if the material produced was too thin

if the material is too thin, more radiation arrives at the detector

the detector sends a signal to the pressure control that the level of radiation is too high

the pressure control makes the gap between the rollers bigger

the bigger gap makes the material thicker until the amount of radiation at the detector decreases to its normal level

62

Explain why radiation emitted from the source must have a greater activity than the background radiation during thickness control?

if the activity of the source is too low then the detector cannot tell the difference between it and the background radiation - the equipment would not function properly

63

Which radiation and half-life is best for controlling paper by the thickness control machine? Why?

alpha, beta or gamma

20 seconds, 150 years or 1,000, 000 years

Alpha - Alpha particles will be absorbed by the paper. Beta and Gamma rays are too penetrating so the pressure control would not be able to sense if the paper was too thick or too thin

150 years - 20 seconds is too short; the emitter would have to be changed too often

1 million years is too long; the activity is too low and the detector would not be able to pick up the radiation emitted from the material and so the equipment would not function properly

64

Which radiation and half-life is best for controlling aluminium by the thickness control machine? Why?

alpha, beta or gamma

20 seconds, 150 years or 1,000, 000 years

Beta - Alpha particles would be absorbed by the aluminium; no radiation would reach the detector. Gamma rays are too penetrating so the pressure control would not be able to sense if the aluminium was too thick or too thin

150 years - 20 seconds is too short; the emitter would have to be changed too often

1 million years is too long; the activity is too low and the detector would not be able to pick up the radiation emitted from the material and so the equipment would not function properly

65

Which radiation and half-life is best for controlling lead by the thickness control machine? Why?

alpha, beta or gamma

20 seconds, 150 years or 1,000, 000 years

Gamma - Alpha and Beta particles would be absorbed by the lead; no radiation woudl reach the detector so the pressure control would not be able to sense if the lead was too thick or too thin

150 years - 20 seconds is too short; the emitter would have to be changed too often

1 million years is too long; the activity is too low and the detector would not be able to pick up the radiation emitted from the material and so the equipment would not function properly

66

What is the activity of a radioactive susbtance?

the activity of a radioactive susbtance is the number of atoms that decay per unit of time

67

In a radioactivity experiment, the count rate of a radioactive substance decreased from 800 counts per second. The half-life of the substance was 40 minutes. What was the count rate after 40 minutes?

400 counts per second (halved)

68

In a radioactivity experiment, the count rate of a radioactive substance decreased from 800 counts per second. The half-life of the substance was 40 minutes. How long would it take for the count rate of the substance todecrease from 800 counts per second to 100 counts per second?

800 to 400 = 40 mins

400 to 200 = 40 mins

200 to 100 = 40 mins

40 + 40 + 40 = 120 mins

= 120 minutes

69

Balance this nuclear equation:

88226Ra → 86226Ra 

88226Ra → 86224Ra + 24He (alpha particles are Helium nuclei)

atomic number decreases by 2, mass number decreased by 4

alpha-emission

70

Balance this nuclear equation:

75187Re → 76187Os

75187Re → 76187Os -10e

mass number stays the same, atomic number decreases by 1

beta-emission

 

71

Balance this nuclear equation:

4399Tc → 4399Tc

4399Tc → 4399Tc 00γ

atomic number and mass number stay the same

gamma-emission

72

What happens if you choose a short half-life?

radiation will decrease quickly toa level lower than background radiation

73

What happens if you choose a very long half-life?

activity continues for longer but may be difficult to spot above background radiation

74

What are the uses of radioactivity?

medical tracers

non-medical tracers

radiotherapy

smoke detectors

archaeological specimens and rocks

75

What source of radiation is used in medal tracers? Why?

Would you use a half-life of 10 mins, 6 hours or 5 months? Why?

Beta and gamma radiation is used in medical tracers because they penetrate the skin and other body tissues - this makes them suitable as medical tracers

6 hours: you would want the blood flow to be able to take it all around the body allowing you to take many pictures. 10 mins is too short for the information and you might want to take repeated readings. 5 months is too long for a person to be radioactive - dangeorus

76

How does medical tracing work?

A source which emits beta or gamma radiation is injected into the patient (or swallowed). The radiation penetrates the body tissues and can be detected externally. As the source moves around the body, the radiographer uses a detector to monitor its progress or get a 'snapshot' of its distribution

A computer converts the reading to an on-screen display showing where the radiation is coming from. Doctors use this method to check whether the organs of the body are working as they should

77

Why would you not use an alpha source is medical tracers?

they would be stopped by the boyd's tissues, so you would never detect it externally

the strong ionising power makes alpha really harmful if it gets inside of you

78

How do smoke detectors work?

The alpha radiation ionises the air particles inside the smoke detector. This allows a small electric current to flow

If there is a fire, smoke particles going into the detector are hit by alpha radiation. This reduces the ionisation of the air particles causing the current to drop

The drop in current is detected by the smoke detector, setting off the alarm

79

Which source of radiation is used in a smoke detector?

Would you use a half-life of 20 mins, 4 months, 10 years or 1000 years? Why?

You would chose alpha because they are more likely to be absorbed by smoke particles. Beta is more penetrating than alpha and would pass straight through the smoke. Gamma is even more penetrating. Gamme and beta would not affect the charge and so the smoke detector wouldn't set of the alarm

10 years - 20 mins and 4 months need to be replaced quickly but 1000 would mean too little radiation coming out - not active enough to detect its radiation from the background radiation

80

How does radiotherapy work?

gamma radiation is used to destroy unwanted cells (cancerous cells.)

81

How do industrial tracers work?

Squirt a gamma radiation source into an underground pipe, let it flow along and fl along the outside with a detector

Gamma radiation will penetrate through a metal pipe, but some of it getts absorbed - exaclty how much depends on the thickness of the pope and what it's made of

If there's a crack in the pipe, the gamma-source will collect outside the pope, and your detector will show extra high radioactivity at that point

the isotope used myst be a gamma emitter so that the radiation can be detected through any rocks or eatyh surrounding the pipe - alpha and beta particles would be tooo easily absorbed

it should also have a short half-life so as not to cause long-term hazard if it collects somewhere

82

What is working out the age of rocks, fossils and archaeological specimens called?

radioactive dating of archaeological specimens and rocks

83

How do scientists date of archaeological specimens and rocks?

by measuring the amount of a radioactive isotope left in a sample, and knowing its half life, you can work out how long the thing has been around

84

What can radiation do to living organisms?

cause mutations

damage cells and tissues

85

Radiation can both ... and ... cancer

Radiation can both cause and cure cancer

86

Which radiation is most dangerous externally? Why?

beta and gamma can penetrate the skin and soft tissue to reach organs inside the body

this makes beta and gamma radiation more hazardous than alpha when outside of the body

87

Which radiation is most dangerous internally?

alpha radiation can't penetrate the skin, but it's very dangerous if it gets inside the body

alpha sources do all their damage in very localised area

if betta or gamma radiation get inside the body (e.g. by being swallowed or breathed in), their radiation mostly passes striaght out without doing much damage

88

What happens when radiation enters your body?

when radiation enters your body, it will collide with molecules in your cells

these collisions cause ionisation, which damages or destroys the molecules

89

What do lower doeses of radiation tend to do inside the body?

lower doses tend to cause minor damage without killing the cell

this can cause mutations in cells which then divide uncontrollably - this is cancer

90

What do higher doeses of radiation tend to do inside the body?

higher doses tend to kill cells completely, causing radiation sickness if a large part of your body is affected at the same time

91

What doee the extent of the harmful affects of radiation depend on?

 the extent of the harmful affects of radiation depends on how much exposure you have to the radiation, and its energy and penetration

92

When can radiation be used to treat cancer? How does this work?

once cancer has started, patients can be given radiotherapy to kill the cancer cells and stop them dividing

this involves using a high dose of gamma rays, carefully directed to zap the cells in the tumour while minimising the dose to the rest of the body

93

Most radioactive waste from nuclear power stations and hospitals is 'high-level'/'low-level'

Give two examples of this

How do you dispose of this waste?

Most radioactive waste from nuclear power stations and hospitals is 'low-level' (slightly radioactive)

e.g. clothing, syringes

this kind of waste can be disposed of by burying it in secure landfill sites

94

'High-level' waste is/is not very dangerous

How do you dispose of it?

'High-level' waste is very dangerous

A lot of its stays highly radioactive for tens of thousands of years, and so has to be treated very carefully

it is often sealed into glass blocks, which are sealed in metal caniseters - these could then be buried deep underground

95

What is the problem with disposing high-level waste?

it is difficult to find suitable places to bury high-level waste

the site has to be geologically stable (e.g. not suffer from earthquakers), since big movements in the rock could disturb the canisters and allow radioactive material to leak out

if this material gets into the groundwater, it could contaminate the soil, the plants, rivers etc... and get into our drinking water

96

How do you minimise your exposure when working with radioactive sources?

never allow skin contact with a source, and always hold it with tongs at arm's length

keep the source pointed away from the body and avoid looking directly at it

store radioactive sources in a sealed lead box whenever not being used

97

What extra precautions do people who regularly work with radioactivity need to take?

medical workers who use radioactivity need to wear lead aprons and stand behind lead screens during procedures

industrial nuclear workers wear full protective suits to prevent tiny radioactive particles being inhaled or lodging on the skin or under fingernails etc...

workers can also use remote-controlled robot arms to carry out tasks in highly radioactive areas

98

Is it possible to predict when an atom might decay?

yes