00:01
This problem is about the photoelectric effect, that is the emission of photo electrons when we use radiation to hit a material.
00:09
So in this case, we are going to use two kinds of radiation, red and green light.
00:15
The problem says that when we use these two radiations to hit the same material, the kinetic energy of the electrons or photo electrons in the green case has a maximum value that is, 1 .5, the maximum value of the kinetic energy when we use red light.
00:37
And we want to compute what is the work function.
00:40
Okay, the equation that we're going to use in order to solve this problem, in this case is just one, is this equation here, that says that the maximum kinetic energy of the photoelectrons is equal to the plank constant, this age that has this value, the speed of light that has this value, divided by the wavelength of the radiation that is heating the material minus the work function.
01:08
As we are using the same material to produce the photo electrons, this work function is the same in both cases for us.
01:21
So if we write again this equation for each case, we will have something like this.
01:27
First, for the red light, we will have the maximum kinetic energy.
01:32
When we use red light is equal to hc divided by lambda r minus the work function and then for the green we have something like this very similar lambda g minus the work function that is the same in both cases okay so we can also use the information of the problem that says that this maximum kinetic energy is 1 .5 okay the maximum kinetic energy in the red case but this maximum synetic energy in the red case is just hc divided by lambda r minus the work function okay so actually these two terms are equal well, okay, this and this...