00:01
For a, the probability of finding the atom between 0 and a over 2 is the probability of finding it less than a over 2.
00:07
So this is equal to the integral from 0 to a over 2 of the wave function 1s squared, which i wrote the wave function above.
00:14
R here is the distance away from the center.
00:16
A is the boar's radius times 4 pi r squared.
00:18
We're dealing with a sphere integrated over dr.
00:21
So let's go ahead and replace that with the psi squared.
00:24
And we're going to pull everything that's not related to r out front.
00:27
So we have 4 over a cubed.
00:33
The square root goes away since we squared it.
00:35
And we saw the integral from 0 to a over 2, e to the minus 2r over a, r squared d .r.
00:55
So i would recommend doing use substitution.
00:59
You could also integrate by parts, or you could just use an integration table.
01:03
To not spend too much time doing this, i chose to go ahead and use an integration table.
01:07
So what we have here is the probability p is equal to 4 over a cubed.
01:22
And this comes out to equal ar squared over 2...