00:02
In this question here, we're going to discuss the photoelectric effect.
00:05
The photoelectric effect is when an electron, which is orbiting some nucleus, there's some sort of positive, there's some sort of attractive potential, some electric potential.
00:19
So to separate these two, the nucleus and the electron, we need to apply some energy.
00:25
And this energy that was acquired to separate them, we call phi, and that is the work function.
00:35
Typically, one way we can supply this energy is with a photon.
00:40
So this red line here is a photon.
00:43
And this photon is absorbed by the electron.
00:47
The energy of the photon is transferred into the energy that allows you to break the attraction between the electron and the nucleus, so the energy for the work function.
00:59
And any excess energy from the photon goes into kinetic energy of the electron.
01:04
So to solve this problem, we look at conservation of energy.
01:09
So the energy before equals the energy after.
01:15
Okay? so what is the energy before? the energy is the energy of the photon, which is equal to planes constant times the frequency, which is equal to h times lambda, no, sorry, which is equal to c divided by lambda, as we have f is equal to as we have the the wavelength times the frequency is equal to the speed of light so the frequency is equal to the speed of light divided by the wavelength okay so that is the energy before the energy after is equal to the work function so the energy that was required to break the bond plus the kinetic energy okay now we see here that the electron is emitted with a velocity of 6 times 10 to the 5 meters per second.
02:17
So we have to ask ourselves, is this relativistic or not? and we divide both sides by c, which is the speed of light, which is 3 times 10 to the 8 meters per second, which is equal to 0 .02.
02:32
So that means that the velocity is small compared to the speed of light, so we can use classical physics and ignore special relativity...