Radiation Flashcards
What is meant by ‘ionising radiation’ ?
Ionising radiation causes electrons to removed from an atom (or molecule).
What is meant by absorbed dose?
Absorbed dose is the energy absorbed per kilogram (of material).
- Ionising radiation carries energy.
- This energy can be absorbed by tissue and cause damage.
- If the energy is concentrated on a small mass, the absorbed dose is greater.
What does the prefix n stand for?
n stands for nano
nano = x 10-9
What does the prefix m stand for?
m stands for milli
milli = x 10-3
List some applications of nuclear radiation.
(at least three)
- chemical tracers to help with medical diagnosis
- killing cancer cells
- sterilising medical instruments
- measuring thickness of materials
- carbon dating
- smoke detectors
What are the three main forms of protection against the effects of radiation?
Time
(the amount of time spent near a source of radiation affects the exposure)
Distance
(the greater the distance from the radiation source, the lower the exposure)
Shielding
(certain materials can limit the exposure to radiation)
What is the radiation weighting factor?
The radiation weighting factor is a number that takes into account the type of radiation to which you are exposed.
What does the prefix G stand for?
G stands for giga
giga = x 109
Name the three quantities shown in this formula.
A = activity
N = number of decays
t = time
What is the unit for energy?
The unit for energy is joules (J)
What is meant by half-life of a radioactive source?
The time taken for half the nuclei in a radioactive sample to decay
OR
The time taken for the activity of a radioactive sample to fall by half its original value
Name the three quantities shown in this formula.
D = absorbed dose
E = energy
m = mass
Give one use of visible light.
- photography
- illumination
- car headlights
- street lighting
What is the charge on a gamma ray?
A gamma ray has no charge - it is a wave, not a particle.
Describe the materials which can be used to block/absorb the three types of nuclear radiation.
Alpha - paper or a few cm of air
Beta - thin sheet of aluminium
Gamma - a few cm of lead or thick concrete
A radioactive source has an activity of 64 MBq (mega becquerels), and a half-life of 2 hours.
What will be the activity of the source after 8 hours?
The activity will be 4 MBq.
Every half-life, the activity falls by half:
Start 64 MBq
2 hours 32 MBq
4 hours 16 MBq
6 hours 8 MBq
8 hours 4 MBq
What is meant by fusion?
Fusion involves two nuclei joining together to make a large nucleus
What is the charge on an alpha particle?
An alpha particle has a positive charge.
What is the unit for mass?
The unit for mass is kilograms (kg)
What is meant by background radiation?
- Background radiation is produced around us all the time: sources include
- certain rocks
- cosmic radiation (from space)
- radon gas in the air
- nuclear waste
- medical applications
- some foods
State a source of man-made (artificial) background radiation.
Sources of man-made background radiation include:
- weapons testing
- waste from nuclear industry
- medical uses (X-ray, CT scan…)
What is the unit for radiation weighting factor, wR ?
There are no units for radiation weighting factor, wR - it’s just a number
What is meant by fission?
Fission means the splitting of a nucleus.
- Normally, fission is carried out with uranium or plutonium
- Fission can be spontaneous (happens randomly) or induced (caused by firing a neutron at a nucleus)
- The nucleus splits into two smaller nuclei
- 2 or 3 more neutrons are released
- Energy is released
What does the prefix µ stand for?
µ stands for micro
micro = x 10-6
What does the prefix M stand for?
M stands for mega
mega = x 106
Which is the most strongly ionising radiation?
Alpha radiation is the most strongly ionising.
Describe what is meant by alpha radiation.
- Alpha radiation is a particle
- It is relatively slow and heavy
- It is made up of 2 protons and 2 neutrons
- It is positively charged
Name the three types of nuclear radiation.
Alpha α
Beta β
Gamma γ
Describe what is meant by gamma radiation.
- Gamma radiation is a wave in the electromagnetic spectrum
- Gamma rays have no mass or charge
- Gamma rays have a very short wavelength and a high frequency
What is meant by the activity of a radioactive source?
Activity of a source is the number of decays per second.
What is the unit for equivalent dose?
The unit for equivalent dose is sieverts (Sv)
What is the unit for absorbed dose?
The unit for absorbed dose is grays (Gy)
What is the charge on a beta particle?
A beta particle has a negative charge.
What does the prefix k stand for?
k stands for kilo
kilo = x 103
Describe what is meant by beta radiation.
- Beta radiation is a particle
- It is the same as an electron - a beta particle is negatively charged
- It is relatively fast and light
What is meant by equivalent dose?
Equivalent dose measures the biological effects of ionising radiations.
It takes into account the type of radiation, the energy carried by the radiation, and how much tissue absorbs the energy.
What is the unit for time?
The unit for time is seconds (s)
What is the unit for activity?
(of a radioactive source)
The unit for activity is becquerels (Bq)
Name the three quantities shown in this formula.
H = equivalent dose
D = absorbed dose
wR = radiation weighting factor
State a source of natural background radiation.
Sources of natural background radiation include:
- rocks
- food
- human body
- cosmic rays (radiation from Sun and outer space)
- radon gas in the atmosphere
