Topic 3-Radioactivity and ionising Radiation Flashcards
Properties of beta
Electron
Light and fast
Moderately ionising
Stripped by thin metal
Properties of gamma rays
Electromagnetic radiation
No mass, very fast
Weakly ionising
Stopped by thick lead or thick concrete
What is a positron
Antiparticle of an electron
Exact same relative mass but different relative charge (+1)
What are the properties of positrons
Same as electrons
Light, fast moving, moderately ionising
Stopped by thin sheet of material
How are positrons obliterated
When collide with an electron at high speeds in annihilation
What are neutrons more penetrating than
Apha, beta and sometimes gamma
Properties of neutrons
Aren’t directly ionising
Absorbed by nuclei of atoms
What happens when an atom absorbs a neutron
Can make nucleus radioactive, then emits ionising radiation
Neutrons are ‘indirectly ionising’
What materials are used to make neutron radiation shielding
They are absorbed by light nuclei, lightest is hydrogen
So hydrogen rich materials water, polythene or concrete are used for radiation shielding
What is added to the shielding and why
Thick lead as neutron absorption can cause nuclei to emit gamma radiation
What four things cause a nucleus to be unstable
1) too many neutrons
2) too few neutrons
3) too many protons and neutrons
4) too much energy
What does a curve of stability show
The number of neutrons in comparison to protons for stable isotopes
An isotope that lies above the line of stability has
Too many neutrons
An isotope below the like of stability has
Too few neutrons
B- decay is
The emission of electrons from the nucleus
What does beta decay happen in (B-)
Isotopes that are “neutron rich” have more neutrons than protons
Nucleus ejects beta particle, one of neutrons changes into a proton
In beta (B-) decay what happens to the proton number and the nucleon number
The proton (atomic) number increases by one and the nucleon (mass) number stays the same
What is beta plus decay
Emission of positron from nucleus
Proton gets changed into a neutron
What happens to the proton number and neutron number in beta-plus decay
Proton number decreases by one the nucleon number stays the same
What does Apha decay happen in
Very heavy atoms e.g uranium and radium
Nuclei to massive to be stable
What happens to the proton number and nucleon number in Apha decay
Proton number decreases by two, nucleon number decreases by four.
Why are gamma rays emitted
After alpha or beta decay the nucleus has excess energy, which it loses by emitting gamma ray
What happens to proton and nucleon number when gamma rays are emitted
Nothing, no change
What is the relative charge of up-quarks
2/3
What is the relative charge of down-quarks
-1/3
What is the relative mass of and up-quark
1/3
What is the relative mass of a down-quark
1/3
What quarks are protons made of
Two up-quarks and one down-quark
What quarks are neutrons made up of
Two down-quarks and one up-quark
What is the charge on a proton in quarks
2/3 +2/3+(-1/3)=+1
What is the mass of a proton in quarks
1/3+1/3+1/3=+1
What is the charge of a neutron in quarks
2/3+(-1/3)+(-1/3)=0
What is the mass of a neutron in quarks
1/3+1/3+1/3=1
When a neutron changes to a proton what quarks does it change
A down to an up
If a nucleus is unstable and converts a proton to a neutron to become more stable what quarks does it change
An up to a down
When a neutron turns to a proton what has to happen and why
Nucleus has to produce a negatively charged particle as well to keep charge zero
Produces an electron
B- decay
When a proton changes to a neutron what has to happen or be produced
Produced a positron to keep the overall charge at +1
How are tracers in medicine used
Radioactive isotope injected or swallowed, external detectors followed progress around the body, computer detects image
E.g iodine-131 is absorbed by thyroid gland, gives out radiation which is detected to see if it is taking iodine as it should
What types of isotopes are used as tracers
Beta or gamma as pass out of body and have short half-lives
How does a PET scan work
1)Inject substance into body (glucose), containing a positron emitting radioactive isotope with short half life-tracer
2)positron meets electrons and annihilates them, emitting high energy gamma rays which are detected
Distribution of radioactivity matched up with metallic activity (more radioactive glucose is taken up by cells and used by those doing more work ) ones with increased metabolism
3)isotopes with short half lives used, made close to where used (hospitals have own cyclotrons) if travel long distance, activity too low and not useful
Properties of alpha
Helium nucleus
Slow and heavy moving
Strongly ionising
Stopped by paper, skin…
What can PET scans be used to diagnose
CHD-show areas of damaged tissue in heart by detecting areas of decreased bold flow —->heart attacks
EPILEPSY-blood flow and activity in brain
CANCER TUMOURS-metabolic activity in tissue, higher than in normal cells due to rate of growth
What can ionisation from radiation lead to
Kill/damage cells so can’t decide—>tissue damage
Alter genetic material in cell—->Mutations
Divide and crow uncontrollably=cancer
What is recommended for treatments to decrease the risks of radiation
Lowest possible dose of radiation
Short exposure time
Wear lead shielding to protect other parts of body not being treated
What should medical personnel do to limit exposure to radiation
Intensity decreases with distance so stand well away or remotely control
Stand behind lead screan
Wear lead-lined clothing
Radiation closely monitored
How is radiation used internally to treat tumours
Placed inside body, into or near tumour
Injecting or implanting small radioactive substance
High dose to small part of body, limit damage to normal cells
How is radiation used externally to treat tumours
High energy x-Rays or gamma rays aimed at tumour
Carefully focused but damage done to healthy cells
What are the benefits of internal sources to treat tumours rather than external
Shorter by up to 6 weeks
Reduces number of visits to hospital
And time to wait to undergo further planned treatment
What is a negative of using radiation internally
Emit radiation after source inserted
Limit contact with people until removed (days later)
Bonus of using external rather than internal radiation
Treatment lasts a few minutes and patient doesn’t emit radiation afterwards
Effects of internal and external radiation
Internal, no side effects but discomfort
External, short and long term effects
Why Aretha’s two types, internal and external
Used often overlap but used to treat different parts of the body
What are some of the social and medal issues with radioactivity and medicine
Damage normal cells—>side effects
Radiotherapy—>hairloss, sickness, skin irritation
Serious—>long term! bowl damage and infertility
Quality of life reduced, some refuse
Rare but second cancer, but without the treatment of first life expectancy shorter
Not always cured, but reduce suffering before death (palliative care)
What is reducing suffering before death known as
Palliative care
Why is developing medical care controversial
New and don’t know long term side effects
Test on cells in lab, then animals, then humans
Patient should be informed of side effects but doctors don’t know them
Ill people want to get on trial but limited spaces
How long till successful treatment it shared???
