00:01
This problem, what we're trying to do is we're trying to find the wavelength of light when we have visible light shining on a metallic surface with a work function of 1 .30 electron volts.
00:14
We know the kinetic energy of the photons coming off of the surface is going to be 0 .92 electron volts.
00:23
And what we're trying to do is we're trying to find the wavelength of the photons or the wavelength of lambda.
00:30
To do this, we're going to use the work function equation.
00:33
So negative work function plus the energy of the photons is going to be equal to the kinetic energy of the photons of the electrons that have popped off the metallic surface.
00:44
So this is going to be negative 1 .3 plus hf is equal to 0 .92.
00:51
And again, these are still an electron volts.
00:53
That's going to be important for later.
00:55
So we have negative 1 .3 electron volts plus planx concept.
01:00
Planck's constant is typically given to us in jules, so it's 6 .63 times 10 to the negative 34 joules times seconds.
01:09
We need to convert that into electron volt.
01:12
So we're going to convert it by multiplying one electron volt is equal to 1 .6 times 10 to the negative 19 joules.
01:21
And that's going to give us electron volts per second, or time second, which is what we want.
01:25
This is then multiplied by frequency and is equal to 0 .19.
01:29
Electron volts...