So the wavelength of green light in the visible spectrum of excited hydrogen atoms is 486.1 nanometers. What is the energy of each photon? So let's do that. So it said it was 486.1 nanometers. So that was the wavelength. So how do we do this? We have to use Planck's equation to do this. So remember Planck's equation? E equals n, h, nu. So first it said 1 photon. And then it says, okay, well, what's the energy of a mole of photons? So we're going to do two problems here. So the first one, since it says 1 photon, n is going to equal what? 1, right? 1. The second one is said a mole of photons. So n is going to equal what? 6.02 times 10 to the 23rd. Okay, so let's just write that down. So wavelength is wavelength in this equation? No. No. So we've got to use the speed of light equation. So we're going to do this equation to a what that equation that we can use. So that equation has wavelength in it, right? So this equation has frequency in it. So what we're going to do is substitute frequency for it here. Okay? So that's the case. We're going to have to solve for frequency. Frequency will see over lambda, like that. Like that. Now we should have everything we need, right? The first n was 1. So let's convert this to meters first. That's it. That's it. We could convert it at the end, too. But let's just convert it now. Do you guys remember how many nanometers there are in a meter? Uh-huh. What did you say? Micro meters. So 1 times 10 to the 9th nanometer. So I'm not impressed with nobody being able to answer them. Okay? So this 1 meter. Nice. Okay, so. So, it's going to be faster. Okay? So. And equals 1. H. Six point six to six. Time to 10 to the negative 34. Joules seconds. 2.998 times 10 to the 8 meters per once again. The wavelength is not any meters, so 1 divided by a wavelength. So doing that, couple of you see, meters cancels. Seconds cancels there. And we've got Joules. Okay? So Joules good energy unit. So just calculated all that. Okay. And again, you should expect this to be a small number because it's one photon today. So in this case, like a four point, I'm adding to 4087 times 10 to the negative 19 joules per, what was it, photon? So we're going to do that one. Okay? So that would be for one photon, but for a mole of photons, right? I'm going to erase everything except for, because we're running short on time. I'm just going to read you this problem except of N being 1. It's N is 6.02 times 10 to the 23rd thermal. So this no longer applies. So this one you would expect to be much bigger because it's a mole with photons as opposed to 1 photon. So you just take that and multiply it by, and to 4, 6, they get 2.4, 6, 1, times 10 to the 1, 2, 3, 4, 5. Yeah. Joules. Mole. That would be screen photons. So that's how much energy a mole gets. Are there any questions on this one? Okay. So sorry I went through that one a little bit. You got to record.