00:01
In this exercise, we want to use a wavelength of 10 nanometers in order to study a biological specimen.
00:06
And in question a, we have to find the ratio between the energy of a photon with this wavelength and the energy, the kinetic energy of an electron with the same wavelength.
00:17
And in order to find this, i'm going to briefly review how we have to proceed in order to find these energies.
00:25
So first, remember that from the debra lee formula, the momentum, of a particle, and this is general for any particle, he's written as h, which is planx constant, divided by lambda.
00:39
And h is equal to 6 .63 times 10 to the minus 34 joules second.
00:49
Now the energy of a photon is proportional to the momentum, so it's equal to the momentum times the speed of light c, which means that the energy of a photon is hc divided by the momentum, lambda.
01:06
The kinetic energy of an electron, on the other hand, is equal to mv squared over 2.
01:15
And remember that for a massive particle, the momentum p can be written as mv, which means that v can be written as the momentum p divided by m.
01:27
So the energy of the electron is m divided by 2 times v, which is p over m, squared.
01:35
So this is p squared over two.
01:36
So this is p squared over two.
01:38
2m.
01:43
Okay...