-average time taken for a substance to decrease by half in terms of activity
-average time take for half of the radioactive atoms to decay
avg time it takes for number of nuclei of isotope in a sample to halve
avg time it takes for count rate from sample containing isotope to fall to half of its initial level
Half life is the term given to describe the amount of time (on average) it takes for the number of unstable nuclei in a radioactive sample to half
Radiation dose: a measure of the risk of harm
Affected by which organs radiation is exposed to
What type of radiation you’re exposed to
Amount of radiation your exposed to
Existing health problems eg skin issues Tukka akhi
The nuclei of radioactive atoms are unstable. They break down and change into a completely different type of atom. This is called radioactive decay. For example, carbon-14 decays to nitrogen-14 when it emits beta radiation.
It is not possible to predict when an individual atom might decay. But it is possible to measure how long it takes for half the nuclei of a piece of radioactive material to decay. This is called the half-life of the radioactive isotope.
There are two definitions of half-life, but they mean essentially the same thing:
- the time it takes for the number of nuclei of the isotope in a sample to halve
- the time it takes for the count rate from a sample containing the isotope to fall to half its starting level
Different radioactive isotopes have different half-lives. For example, the half-life of carbon-14 is 5,715 years, but the half-life of francium-223 is just 20 minutes.