8. (30 pts)
a) (10 pts) If the half-life of a certain radioactive element is 1000 years, how much of a 5000 kg lump
of the stuff will be left after 2000 years?
One half of the parent goes away every 1000 years. So after 1000 years there is 2500 kg left. After
another 1000 years there would be 1250 kg remaining.
b) (10 pts) Balance the nuclear reaction equation for beta decay of lead-214 listed below: (Fill in appro-
priate values for the two blanks.)
82Pb214 ⇒83 Bi 214 +−1e0+0ν0
c) (10 pts) Every fundamental particle has an associated anti-particle. For example, the anti-particle
associated with the electron is the positron. Each anti-particle has the same mass but opposite charge
of the “regular” particle. What happens when an anti-particle and “regular” particle combine?
When a particle and its anti-particle combine, they are completely anihilated and release (lots of)
energy.