P7.5 - Activity And Half Life (Finished) Flashcards
What is the activity of a radioactive source?
The activity of a radioactive source is the number of unstable atoms in the source that decay per second.
What is the unit of activity of a radioactive source and what does it stand for?
The activity of a radioactive source is measured in Becquerel, which is 1 decay per second
Radioactive decay is a ___ process
Random
How do you monitor the activity of a radioactive sample?
You can measure the activity of a radioactive sample with a geiger counter by measuring the count rate (no of counts/second) from the sample which is proportional to the activity of the source
What is the half-life?
The half-life is the time taken for the number of radioactive nuclei in an isotope to halve; also the activity and count rate
What can the half-life be used for?
Half-life can be used to make predictions about radioactive sources
Every time the radioactive nucleus ___ to become a stable nucleus, the ___ as a whole will ___
Decay, activity, decrease
What does a short half-lofe and long half-life mean?
A short half-life means the activity falls quickly as the nuclei are unstable and rapidly decay
A long half-life means the activity falls slowly as most nuclei don’t decay for a long time
What is an advantage and disadvantage for a short half-life (safety)?
Sources with a short half-life are dangerous due to the high amount of radiation they emit at the start but quickly become safe
What is an advantage and disadvantage of a long half-life (safety)?
A source with a long half-life is safer as it emits less radiation but lasts a long time so nearby areas are exposed to radiation for millions of years
How do you calculate the count rate after n half-life?
Initial count rate / 2^n = count rate after n half-lives
How do you measure half-life from a graph?
Find the time interval that corresponds with a halving of the activity
