00:01
In this exercise, we have an electron that's passing through a slit that has a width of 85 nanometers.
00:07
And we want to find what is the uncertainty of the y component of the velocity of the electron, that is the component in the direction of the width of the slit, delta vy.
00:20
In order to calculate that, i'm going to use the heisenberg uncertainty principle that tells us that the uncertainty in the momentum times, the uncertainty in the position is greater or equal than h -bar over 2.
00:37
Now notice that the uncertainty in the momentum is equal to the mass of the electron times the uncertainty in the speed.
00:46
This is the uncertainty in the momentum in the y direction.
00:50
So this is m times the uncertainty of the y component of the velocity of the electron.
00:57
And so, well, if we substitute this in the heisenberg uncertainty principle, we get that m times delta v .y times delta y is greater or equal than h bar over 2.
01:12
Notice that delta y here, the uncertainty in the position, is the width of the slit because the electron could be anywhere in the slit...