( a ) ( i ) What is meant by the term 'radioactive decay'? ( ii ) State TWO properties of alpha (α) particles. ( b ) A radioactive isotope has a half-life of 8 days. A freshly prepared sample of the isotope has an activity of 4.8 × 10⁴ disintegrations per second. ( i ) Calculate the decay constant of the isotope. ( ii ) Determine the activity of the sample after 32 days. ( iii ) Calculate the number of atoms of the isotope present in the sample initially. ( c ) State ONE use of radioactive isotopes in medicine.