00:01
Variant has a half -life of about two minutes.
00:03
Suppose you obtain a sample weighing 10 grams, and it takes 10 minutes to set up the experiment.
00:09
How many grams of barium 122 will remain at the point in which you begin the experiment? so we're going to need two equations.
00:18
The first is nt equals n0 times e to the negative lambda over t, or times t, now what this is, all of these variables, n to the t is the amount remaining, n to the zero is the starting amount.
00:55
T, that's your time.
01:00
Now, lambda, lambda is the decay constant for a particular radio isotope.
01:14
Since it wasn't given in the problem, we're going to have to figure it out for ourselves.
01:20
So lambda is just equal to the natural logarithm of two divided by the half -life.
01:27
Now the half -life we were told was two minutes.
01:30
So this would make lambda a natural logarithm of two divided by two minutes.
01:36
So we would just take the natural logarithm of two, divided by two, and this will give us 0 .34657.
01:46
And this is in minutes.
01:48
So now let's put that back into our equation with the rest of our givens.
01:56
We're looking for nt.
01:59
Our starting amount was 10 .0 grams.
02:03
We have e to the minus 0 .3467, and our time was 10...