Doctors use radioactive sources as tracers for medical imaging. The table below shows the properties
of some radioactive sources. Which source would be the best to use for a tracer that must be injected
into the body?
Enter your answer as a number
Radioactive source
Type(s) of
radiation emitted
Half-life
1
gamma
7 weeks
2
beta
3 days
12 minutes
3
alpha and gamma
4
gamma
23 minutes
5
alpha
4 hours