Nuclear Decay A levelWatch
Technetium-99 (Tc-99) is a radioisotope tracer with a decay constant of 0.12 hr^-1 . It emits 140 keV gamma photons and is commonly used in nuclear medicine to study the functionality of body organs and systems. A patient undergoing a bone scan is injected with Tc-99 with activity 800MBq. After how long will the total amount of gamma energy emitted from the patient every second fall to 1.0 micro jules
Now, for the activity of the substance after time
We need the time when activity is less than 1 microjoule.
So we calculate how many decays per second we need for this energy to be true, if each decay gives off a single photon and we need ;
Now we have , and
Take logs of both sides