What is radioactive decay?
A spontaneous process where an unstable atomic nucleus changes to become more stable
It releases particles known collectively as radiation.
Name the three types of radiation.
- Alpha decay
- Beta decay
- Gamma decay
Each type of radiation is associated with different processes and particles.
What occurs during alpha decay?
A heavy nucleus ejects an alpha particle (2 protons and 2 neutrons)
Heavy elements like uranium and americium are alpha emitters.
What happens during beta decay?
A neutron turns into a proton and a beta particle (electron) is emitted
This occurs in nuclei with too many neutrons.
What is released during gamma decay?
A gamma photon
This process does not change the nuclear configuration of the parent nucleus.
How do alpha particles interact with materials?
They are very easily blocked due to their mass, charge, and kinetic energy
A single alpha particle can cause ionisations before being stopped.
What is the decay constant?
The probability of a given particle decaying in one second
Its value must be between 0 and 1.
What does activity measure?
The number of decay events per second
It is measured in Becquerels.
What is the physical half-life of a substance?
The time taken for the initial number of undecayed particles to reduce by half
It can be calculated using the decay constant.
What type of relationship describes the decay of undecayed particles?
Exponential decay
As the number of undecayed particles decreases, the rate of decay also decreases.
What is biological half-life?
The time taken for the concentration of a foreign compound in the body to fall by half
For example, the active drug in a headache tablet is removed by the liver.
Define irradiation.
Exposure to ionising radiation
It differs from contamination, which is the presence of harmful radioactive material.
What is radiation sickness?
Effects similar to severe sunburn, including fatigue, fainting, and confusion
It can be fatal if the radiation dose is too high.
What is direct ionisation?
When charged particles add or remove electrons from atoms
Examples include alpha or beta particles.
What is indirect ionisation?
When uncharged particles, like gamma photons, create ion pairs by being absorbed
This can occur further within a living organism.
What can happen when DNA is ionised?
It can lead to mutations
Most mutations are harmless, but some can cause cells to proliferate, forming tumours.
What are radiopharmaceuticals?
Radioactive substances designed to be introduced into the body
They are used as tracers for diagnostics and in drugs for therapeutic purposes.
Give an example of a radioisotope used as a tracer.
Technetium 99m
It can be attached to various compounds taken up by different parts of the body.
What is internal radiotherapy?
Brachytherapy, where a tiny radioactive source is placed inside or near a tumour
It kills nearby cancer cells.
What is external beam radiotherapy?
Directing a beam of X-rays from outside the body towards a tumour
This is done from multiple angles.
When imaging, what type of emitter is used?
Only gamma emitters
They can pass through several centimeters of bodily tissues.
What is the advantage of using radiation for sterilisation?
Equipment can be sterilised without removing it from its packaging
This is particularly useful for surgical instruments.
