 So the wave length of green light in the visible spectrum of excited hydrogen atoms is 486.1 nanometers. What is the energy of each photon? Okay So let's do that So it said it was 486.1 Wait, right? 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. Okay, so first it said one photon and then it says okay. Well, what's the Energy of a mole of photons. Okay, so we're going to do two problems here So the first one since it says one photon and it's going to equal what? One right one the second one is that a mole of photons. So and it's going to go what? 6.022 times 10 to the 23rd. Okay, so let's just write that down so Wavelength is wavelength in this equation No, so we've got to use the speed of light equation To convert this equation to a what that equation that we can use So that equation has wavelength there right so this equation has frequency in it So what we're going to do is substitute frequency for here. Okay, so that's the case. We're going to have to solve for frequency Frequency will see over lambda like that and then plug it into this equation here like that Now we should have everything we need right the first n was one Let's convert this to meters first 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? What what do you say? So not Micrometer systems so one times 10 to the 9th nanometer so I'm not impressed with nobody being able to answer them This one meter equals one h 6.626 times 10 to the negative 34 Joel seconds 2.998 Times 10 to the 8th meters for one second And the wave length is that many meters so One divided by a way point doing that. Hopefully you see meters cancels Seconds cancels there and we've got joules Okay, so joules good energy on units. So just calculate it all out So and you should expect this to be a small number because it's one Photon so in this case I got four point I'm adding to 407 Times 10 to the negative 19 joules per 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 one It's n is 6.022 times 10 to the 23rd per mole. So no longer applies So this one you would expect to be much bigger because it's a mole of photons as opposed to One photon Are there any questions on this one, okay, so sorry I went through that You got it recorded