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Physics > Radiation and Instability COPY > Flashcards

Radiation and Instability COPY Flashcards

1
Q

What is alpah radiation?

A

A helium nucleus

42He

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2
Q

What is beta radiation?

A

e-

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3
Q

What is gamma radiation?

A

A high-energy photon

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4
Q

What material is needed to stop alpha radiation?

A

Paper/skin

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5
Q

What is the typical speed of alpha in air?

A

106 - 107 ms-1

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6
Q

What is the approx. no. of ion pairs per mm of air for alpha?

A

104

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7
Q

Is alpha radiation deflected in an electric field?

A

Yes

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8
Q

Is alpha radiation deflected in a magnetic field?

A

Yes

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9
Q

What is the distance travelled in air for alpha?

A

a few cm

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10
Q

What is the typical speed of beta radiation in air?

A

108 ms-1

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11
Q

What is the approx. no. of ion pairs per mm of air for beta?

A

102

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12
Q

What material is needed to stop beta?

A

3mm of aluminium

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13
Q

Is beta radiation deflected in an electric field?

A

yes

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14
Q

Is beta radiation deflected in a magnetic field?

A

yes

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15
Q

What is the distance travelled in air for beta?

A

up to 1 m

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16
Q

What is the typical speed in air of gamma?

A

3 x108 ms-1

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17
Q

What is the approx. no. of ion pairs per mm of air?

A

1

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18
Q

What material is needed to stop gamma?

A

Not even lead can stop it completely

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19
Q

Is gamma radiation deflected in an electric field?

A

no

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20
Q

Is gamma radiation deflected in a magnetic field?

A

no

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21
Q

How far can gamma travel in air?

A

Depends on the source

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22
Q

Why do the different types of radiation travel a different distance in air?

A
  • alpha ionises ionises more than beta or gamma
  • This is because it has double the charge of beta
  • alpha travels slower than beta and so spends more time near the atoms that can be ionised
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23
Q

How does ionising radiation affect living cells?

A
  • damages vital molecules directly or by creating free radicals in the cells which react with vital molecules
  • normal cell division is affected and cell membranes can become damaged
  • As a result cells die or mutate
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24
Q

What is irradiation

A

Where the source is outside the body and the radiation from it hits the body

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25
Q

How can irradiation be lessened?

A
  • shielding
  • keeping the source a large distance away
  • short time of exposure
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26
Q

What is incorporation?

A

Where the source of radiation is inside the body

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27
Q

How can incorporation be lessened?

A
  • Seal the radioactive source
  • Wear protective clothing like dust masks or gloves
  • Keep handling time as short as possible
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28
Q

Define backgroud radiation

A

The radiation present when there are no artifical sources present

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29
Q

What are the 6 most commom sources of background radiation?

A
  • Cosmic rays
  • radon gas
  • rocks and soils
  • building materials
  • fallout from nuclear testing and nuclear power accidents
  • food
30
Q

Describe cosmic rays as a source of background radiation

A
  • High energy particles from space
  • Atmosphere blocks most
31
Q

Describe radon gas as a source of background radiation

A
  • Caused by the decay of radium in the rocks
  • radioactive gas in the atmosphere
32
Q

Describe rocks and soils as a source of background radiation

A
  • Radiation can be emmited from rocks (like granite) and soils
33
Q

Describe building materials as a source of background radiation

A

Clay contains radioactive materials

34
Q

Describe fallout from nuclear testing and nuclear power station accidents as a source of background radiation

A
  • There is still some radiation in the atmosphere from these events
35
Q

Describe food as a source of background radiation

A

some foods e.g. bananas and brazil nuts are radioactive

36
Q

What are the three main safety tips when handling radioactive sources?

A

1) time: minimise the time that the source is out of its shielded container, and minimise the time that you are handling the source
2) space: put as much distance between yourself and the source as possible. Handle the source with long-handled tweezers or tongs
3) shielding: store the spource in a properly shielded, locked container when not on use. Place proper shielding between you and the source if you have it out of the container

37
Q

Describe how you would identify which type of nuclear radiation is present in a source

A
  • Record background radiation count rate when no source is present
  • Place unknown source neat to a Geiger-Muller tube and record the count rate
  • Place a sheet of paper between the source and the Geiger- Muller tube. Record the count rate. If the count rate drops alpha is present.
  • In additions to the paper, add a 3mm thick sheet of aluminium between the source and the tube and record the count rate. If it drops beta is present.
  • For each count rate that is recorded, take away the count rate of the background radiation to find the actual count rate. If the count rate is above background, gamma is present.
38
Q

What are the uses of gamma radiation?

A
  • Medical tracing
  • Detecting cracks in metal pipes
  • Ionising radiation therapy
39
Q

How is gamma used to detect cracks in metal pipes?

A
  • Either pass gamma through pipe walls during manufacture, or pass radioactive ‘dye’ through the pipe underground.
  • Where the reading on the Geiger counter is higher than normal, there is likely to be a crack in the pipe.
40
Q

What is the main use for alpha radiation?

A

Alpha smoke alarms

41
Q

Explain how alpha smoke alarms work

A
  • The alpha particles emitted by Am-241 collide with oxygen and nitrogen in the air in the detectors ionisation chamber to produce ions
  • A low-level electric voltage applied across the chamber is used to collect the ions, causng a steady and small elecric current to flow between two electrodes.
  • When smoke enters the space between these electrodes , alpha is absorbed by the smoke particles
  • this causes the rate of ionisation and the current to drop, which sets of an alarm
42
Q

What is beta radiation used for?

A
  • Automated paper thickness
43
Q

Explain how automated paper thickness works

A
  • Machine is programmed to maintain a certain count rate which delivers the required thickness
  • If the count rate is too low, the paper is too thick, and so the rollers are moved closer together
  • If the count rises the rollers are moved further apart
44
Q

Why is beta the best source for automated paper thickness?

A
  • Alpha would not go through the paper
  • The intensity of gamma would not change much with the thickness of the paper
45
Q

What is radioactive decay?

A

A random, naturally occuring emission of radiation by an unstable parent nucleus in an attempt to be more stable.

46
Q

What is the equation for the alpha decay of 22688Ra to radon (Rn)?

47
Q

How can you calculate the kinetic energy of the products of alpha decay?

A

Multiply the mass difference by the speed of light squared

48
Q

Write the equation for thr beta- decay of Carbon-14

49
Q

What happens during beta- decay?

A

A neutron decays to a proton

50
Q

What is the equation for the beta+ decay of 3015P to Si?

51
Q

What happens during beta+ decay?

A

A proton turns to a neutron

52
Q

Write an equation for the neutron emmision when helium and 23892U react to Pu

53
Q

Write an equation for the proton emission of 53Li to helium

54
Q

Write the equation for the electron capture that turns 6429Cu to Ni

55
Q

Why is a photon released during electron capture?

A

When the electron is absorbed by the nucleus, there is a vacancy in the first shell of the atom.

An electron from the second shell moves down to the first which results in an emitted electron

62
Q

Why is beta - decay above the nuclear stability curve?

A

The neutron to proton ratio is too high

so it decays converting a neutron to a proton

63
Q

Why is beta + decay below the nuclear stability curve?

A

The neutron to proton ratio is too low

it decays converting protons to neutrons

64
Q

All nuclei above what proton number are unstable?

65
Q

Do neutron emitters lie above or below the curve?

66
Q

Do proton emitters lie above or below the curve?

67
Q

What points does the nuclear stability curve cross?

A

(20,20)

(60,80)

(80,120)

68
Q

Draw the nuclear stability curve, labelling B-, B+ and alpha emitters

69
Q

How can artificial radioactivity be created?

A

Bombard elements with high energy particles

70
Q

Describe gamma ray emission

A
  • A parent nucleus decays to a daughter nucleus
  • if the daughter isn’t in the ground state it will emit gamma rays at the instant when the daughter nucleus decays to the ground state
71
Q

What is technetium 99 used for?

A

In hospitals as a radioactive tracer

72
Q

What makes technetium good for use as a tracer?

A
  • It is a gamma only emitter

this is good as alpha and beta are not only much more dangerous but wouldnt pass out of the body

  • Has a half life of 6 hours

if it were longer then the body will experience too much exposure which can damage cells. if it were shorterit would decay before it reached the desired organ.

Physics (15 decks)

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