nuclear decay is spontaneous → we will not know exactly when particular nucleus will decay
- however every nuclide has fixed rate of decay
can make predictions abt decay of large numbers of a nuclei of a particular nuclide bc it has fixed half life value
Definition
- half life of a radioactive nuclide is the time taken for half the nuclei of that nuclide in any sample to decay
- PhysicsDefinitions
e.g. half life of iodine-131 is 8 days.
decay curve is graph of number of atoms or count rate against time.
count rate of radioactive substance decreases until all the substance has decayed.
typical background radiation count is abt 18counts/min
- implies that the almost constant rate of 20counts/min is due to the background radiation and the sample has decayed to the point that is radioactive is negligible.
