00:01
We have a k -alpha x -ray emitted from a sample with an energy e of 7 .46 k -ev, which is 7 .46 times 10 to the third electron volts.
00:12
So the energy of an electron e is equal to planks constant times the frequency.
00:17
And to find the z number, we're going to use mostly's law, which says that the frequency is equal to 2 .48 times 10 to 15 hertz times z minus 1 squared.
00:26
So we can replace frequency with energy divided by planks constant, since we know the energy, and solve for z.
00:34
So we have here is z minus 1 is equal to the square root of the frequency divided by 2 .48 times 10 to the 15 hertz.
00:51
But again, frequency is energy divided by planks constant.
00:53
So this is e divided by f, or excuse me, divided by h times 2 .48 times 10 to the 15 hertz.
01:25
So then to get z by itself, we can add one to both sides...