Production, uses and risks of ionising radiation from radioactive sources

Question 1

explain the social and ethical issues relating to the use of radioactive techniques in medical physics

Answer 1

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Question 2

Describe the properties of alpha radiation

Answer 2

+2 charge, 4 mass, heavily ionising, low penetrating, affected by magnetic field

Question 3

Describe the properties of beta (B-) radiation

Answer 3

-1 charge, 1/1840 mass, weakly ionising, low penetration stopped by thin aluminium, affected by magnetic field

Question 4

Describe the properties of gamma radiation

Answer 4

0 charge, 0 mass, not directly ionising, very high penetration, stopped only by thick led, not affected by magnetic field

Question 5

Describe the properties of positron (B+) radiation

Answer 5

+1 charge, 1/1840 mass, weakly ionising, low penetration, stopped by thin aluminium, affected by magnetic field

Question 6

Describe the properties of neutron radiation

Answer 6

0 charge, 1 mass, not directly ionising, high penetration, not affected by magnetic field

Question 7

explain why a atom has a neutral charge

Answer 7

has the number of protons and electrons. this means it has the same number of positive and negative charge, so the atom is neutral

Question 8

Describe the process of B- decay

Answer 8

a neutron within an unstable nucleus decays to give a proton and an electron; this electron is emitted at high speed as a beta particle

Question 9

Describe the process of B+ decay

Answer 9

a proton in the nucleus decays to a neutron and a positron; the positron is ejected from the nucleus at high speed carrying +1 charge away but having almost no effect on the mass of the nucleus

Question 10

Explain the effects on the atomic (proton) number and mass (nucleon) number of radioactive decays

Answer 10

alpha: mass number -4, charge of nucleus -2
beta-:mass of nucleus no change, effect on charge of the nucleus increased by 1
beta+: mass of nucleus no change, charge of nucleus reduced by 1
gamma: no effect on either mass or overall charge of a nucleus

Question 11

Use given data to balance nuclear equations

Answer 11

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Question 12

Describe the features of the N-Z curve for stable isotopes

Answer 12

shows the ratio between the number of neutrons (N) and the number of protons (Z) in the nucleus.

Question 13

Identify isotopes as radioactive from their position relative
to the stability curve

Answer 13

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Question 14

nuclei with high values of Z (above 82) undergo what decay

Answer 14

nuclei with high values of Z (above 82) usually

undergo alpha decay

Question 15

an isotope above the curve will do what

Answer 15

an isotope above the curve has too many neutrons to be stable and will undergo decay

Question 16

an isotope below the curve will do what

Answer 16

an isotope below the curve has too many

protons to be stable and will undergo B+ decay

Question 17

what do the proton and neutron each contain

Answer 17

the proton and neutron each contain three particles called quarks

Question 18

Describe the arrangement of up and down quarks in

protons and neutrons

Answer 18

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Question 19

Use given data to explain the arrangement of up and
down quarks in protons and neutrons in terms of charge
and mass

Answer 19

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Question 20

Explain B- decay

Answer 20

a process that involves a down quark changing into an up quark (a neutron becomes a proton and an electron)

Question 21

Explain B+ decay

Answer 21

a process that involves an up quark changing into a down quark (a proton becomes a neutron and a positron)

Question 22

nuclei that have undergone radioactive decay do what

Answer 22

nuclei that have undergone radioactive decay often undergo nuclear rearrangement with a loss of energy as gamma radiation

Question 23

Describe the dangers of ionising radiation in terms of tissue damage and possible mutations

Answer 23

ionising radiation can kill cells. if small numbers of cells are killed the organism can recover by replacing destroyed cells. if large numbers of cells are destroyed by exposure to large doses of ionising radiation, then the organism cannot recover. can also cause mutations in the DNA in cells. in this case the ionising radiation does not kill the cell but it makes it work different way. it may cause the cell to grow uncontrollably causing a tumour.

Question 24

Explain the precautions taken to ensure the safety of people exposed to radiation, including limiting the dose for patients and the risks to medical personnel

Answer 24

wearing protective clothing, increasing the distance form the source for ionising electromagnetic radiation, and reducing length of exposure

Question 25

Compare and contrast the treatment of tumours using radiation applied internally or externally

Answer 25

some treatments involve x-rays or gamma rays not the patient form an external machine, but this can destroy healthy tissue as well as cancers. if patient takes radioactive materials internally the radiation can be targeted at the tumour and damage to surrounding tissue is reduced.

Question 26

Describe palliative care including the use of radiation in some instances

Answer 26

some conditions are untreatable and some will result in the patient dying palliative care involves minimising the suffering caused by the condition. e.g. radiation can be used to shrink tumours. ethics require consideration of the quality of life of the patient during palliative treatment.

Question 27

Explain some of the uses of radioactive substances in diagnosis of medical conditions, including PET scanners and tracers

Answer 27

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Question 28

Explain why isotopes used in PET scanners have to be produced nearby

Answer 28

as the tracers decay very quickly it is necessary to produce them close to the hospital where the PET scan is carried out.