00:01
In order to identify what the cathode is made of, you'll need to find what is the work function of the particular catalogue.
00:11
So we're going to work with two different scenarios in which the category is used.
00:17
So the first one is that given a photon of wavelength that is 400 nanometers, we have a particular stopping potential, and we just call this v -stop.
00:31
But if we change the wavelength to 300 nanometers we have the stopping potential increasing right so the original v stop is 25 .7 % of the stopping potential over here so if you stop is to 25 .7 % of the stopping potential over here.
01:16
So we need to have two equations and we try to find out what is the unknowns.
01:24
So to equate the wavelength, we need to use the energy of the photon.
01:32
It's equivalent to the work function plus q, which is the charge of electron multiplied by the stopping potential.
01:50
For the first case with 400 nanometers, the energy is hc over lambda.
02:03
We get e0 plus q times 25 .7 times v stop prime.
02:19
This is our first equation.
02:24
For the second equation, we have the wavelength to be 300 nanometers.
02:44
So this is our second equation.
02:49
First thing we want to do is to solve for e0, the stopping potential, sorry, the work function, that's the important value that we need to identify our metal wave.
03:05
So what we're going to do is we're going to substitute in our equation from here, from equation 2, we isolate out what is q times v.
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