An isotope Iodine-123 (53123I^{123}_{53}\text{I}53123I) is a gamma emitter widely used as a radioactive tracer in medical diagnostics, particularly for assessing thyroid function.
State two distinct reasons why a tracer that only emits gamma radiation is preferred for internal medical imaging over tracers that emit alpha or beta radiation.
An Iodine-123 tracer sample is prepared with an initial activity of 240 MBq240\text{ MBq}240 MBq. The half-life of Iodine-123 is 13.2 hours13.2\text{ hours}13.2 hours.
Calculate the number of Iodine-123 nuclei initially present in this tracer sample.
Calculate the time, in hours, required for the activity of the tracer to decrease to 5.0%5.0\%5.0% of its initial activity.
