PAG 7.3 Determining Hlaf-life Using an Ionisation Chamber Flashcards
What is half life?
The half life of a radioactive sample is time taken for the number of radioactive nuclei in the sample to decay to half its original value
Does the half-life of radioactive substance change?
The half life of a radioactive substance is constant for a given sample, and so it does not change with time
What are the two charged terminals of an ionisation chamber called?
Anode and Cathode
What happens when ionising radiation is incident on the gas particles in the chamber?
The ionising radiation will ionise the gas particles, causing them to become charged
What name is given to the current that flows due to the ionisied gas particles
The flow of the charged ions in teh ionisation chamber is known as the ionisation current
Describe the relationship between ionisation current and the intensity of the radiation
The ionisation current is proportional to the intensity of the radiation, since it is related to the number of ions that are formed as a result of the radiation
How can the ionisation current be measured?
The ionisation current will be very small and so to measure it a picoammeter should be used
How can the half-life be determines from a graph of ionisation current against time?
The half life is the length of time it taken for the ionisation current ot halve. this should be a constant value so if possible it should be checked for multiple half-lives on graph
Describe the graph of ionisation current against time that should be obtained
The relationship should show an exponential decay and so will be a downwards curve.
Why does background radiation not need to be adjusted for when determining half-life?
Background radiation levels are relatively constant and very low, meaning they wont affect the value you obtain for half-life
Why may your graph not show a perfect exponential relationship?
Although radioactive half life is consant, radioactive decay is radom and so for a relatively short time period, there may be variations
Why may an old radioactive source be unsuitable for this experiment?
Depending on the soucre’s half life and age, the activity of the source may be too low to obtain a measureable ionisation current
What safety precautions must be taken when working with a radioactive source?
- Limit exposure time
- warning signs when soucre in use
- keep an arm’s length away at all times and handle using long-handled tongs
aHow should a radioactive source be handled safely?
Long handled tongs should be used to handle the source and you should be an arm’s length away at all times
How should a radioactive source be stored safely?
Radioactive sources should be locked away in a sealed lead container
A hazard symbol should be visible on the container as well as the location where it is stored
