What is activity?
The rate at which a source of unstable nuclei decays
Measured in becquerel(Bq)
What is count-rate?
Count-rate is the number of decays recorded each second by a detector
What can be used to measure the count-rate?
A Geiger-Muller tube
What is half-life?
The amount of time it takes the number of nuclei of the isotope in the sample to halve
What are the three types of radiation?
•alpha
•beta
•gamma
What is an additional cause of radiation?
neutrons
Properties of alpha radiation
- consists of two neutrons, two protons (like helium)
- overall +2 charge
- does not penetrate far into materials(can be absorbed by a single sheet of paper)
- highly ionising
- has a range of a few cm in the air
- deflects towards the negative pole of an electric field
- uses; smoke tracers
Properties of beta radiation
- consists of a high speed electron
- has a -1 charge
- moderately ionising
- range of a few m in the air
- penetrates moderately far into material (further than alpha), can be absorbed by a thin sheet of metal(aluminium)
- uses; medical tracing
Properties of gamma rays
- part of the EM spectrum
- typically after alpha or beta radiation to transfer energy
- waves that penetrate far into materials, can be absorbed by concrete or thick sheets of lead
- weakly ionising
- uses; radiotherapy, medical tracers
Define irradiation
the process by which an object is exposed to radiation
Define contamination
the unwanted presence of a material containing radioactive atoms on other materials
Give natural sources of background radiation
- cosmic rays
- rocks
- radon gas
Give man made sources of background radiation
- nuclear weapon testing
- nuclear accidents
What may levels of radiation be affected by?
- location
- occupation
What determines how harmful radiation is?
- type of radiation e.g. ionising-cause mutations in cells
where you’re exposed to it: outside=most harmful → beta/gamma
on/inside the body= most harmful → alpha
the amount(dosage):
• distance from the source
• how long you’re exposed for
• how radioactive the substance is
Explain uses of radiation in medicine
radiotherapy: can be used to kill off cancer cells, can be external(gamma rays) or internal(beta source inside the body)
• can cause radiation sickness
• damages other healthy cells
medical tracers: can be used for detection as the movement of isotopes is tracked around the body, can check if particular organs work properly depending on how much the organ absorbs
•typically gamma, but beta can also be used
Why would you use an isotope with a short half-life?
only emit radiation for a short period and then stop being harmful
What is nuclear fusion?
a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy
Where does nuclear fusion happen? why?
in stars because it required extremely high temperature(hence high levels of energy)
What is nuclear fission?
the splitting of an unstable nucleus to two smaller nuclei
Where does nuclear fission happen?
In nuclear power stations
Why is nuclear fission a chain reaction?
it releases other neutrons and energy(in the form of gamma rays) which means these neutrons can be absorbed by another nucleus and this would cause the nucleus to spilt into smaller nuclei
