half life

Cards (14)

what do radioactive substances do?
give out radiation no matter what
how is radiation measured?
Geiger-Muller tube and counter - which records the count rate
what is count rate?
the number of radiation reaching it per second
Is radioactive decay random or systematic?
random
what can you find out?
the time it takes for an amount of radiation of a substance to halve - half life
how can it be used?
to make predictions about radioactive sources?
what can half life be used to measure?
the rate at which a source decays - measured in Bq - becquerels
what happens each time a radioactive sample decays?
the activity as a whole decreases
what is half life?
The time taken for the number of radioactive nuclei in an isotope to halve
what is the other definition for half life? 
the time taken for the activity or count-rate to half
what is a short half life?
when the activity falls quickly because the nuclei are very unstable and rapidly decay
why are substances with a short half-life dangerous?
because of the high amount of radiation they emit at the start, but they quickly become safe.
what is a long half-life?
the activity falls slowly - most of the nuclei don't decay for a long time
the source just emits small amounts of radiation for a long time
why are substances with a long half-life dangerous?
nearby areas are exposed to radiation for millions of years