00:01
So this question deals with the radioactivity of oxygen 15.
00:05
It has a very short half -life of two minutes.
00:08
If there's the delay of 3 .5 minutes, we want to know what the initial activity of an oxygen 15 sample must be, such that when a p .e .t scan or pet scan is happening, and it requires 0 .5 miliky per liter.
00:26
Yeah, so we need to find in this scenario what our initial activity is for a scan to require this amount.
00:35
So if we can start with our decay rate equation, again, the values you use here can be other number of particles, like activity, mass, et cetera, everything would decay at the same rate.
00:50
So while this is our normal equation, we can just represent this the opposite way where we're trying to solve for initial activity just by multiplying both sides by e to lambda t.
01:02
So positive exponential here, because we're switching these around by multiplication of equally both sides...