in this video we're going to do a quick review of the formulas you need to know if you're studying atomic theory things like wavelength frequency speed of light energy of a photon and so forth so here's the first equation you to be familiar with C is equal to Lambda * new C represents the speed of light it's 3 * 10 8 m/s Lambda this represents the wavelength and the Greek letter new that's the frequency so if we need to calculate wavelength using that formula it's equal to the speed of light divid by the frequency the frequency is going to be the speed of light divided by the wavelength now the next equation you need to be familiar with is this one e is equal to H * the frequency e represents the energy of a photon H is a constant specifically planks constant and it's equal to 6626 * 10 -34 JW * seconds the frequency has the units Hertz or seconds to Theus one now keep in mind the speed of light is equal to the wavelength time the frequency solving for the frequency we get it's equal to the speed of light / Lambda now we could replace the frequency with what we have here and we can get the energy of the photon in terms of starting from its wavelength so that's H C over Lambda so if you know the frequency of light you can calculate the energy of those light particles which will be the photons that represent those light particles if you know the wavelength of light you could use this formula to calculate the energy now typically you're going to be given the wavelength in nanometers and so you need to remember that 1 nanometer is equal to 1 * 10 - 9 M so if your wavelength is let's say 450 nanom you could just plug into your calculator 450 * 109 m into this formula to get the energy of the photon now the next equation we're going to talk about has to do with the photo electric effect so let's say we have a piece of metal and we have electrons on this metal and we decide to shine either blue light or ultraviolet light if those light particles have enough energy they can knock off the electrons from that metal the kinetic energy of the ejected electron is equal to the difference between the energy of the incoming Photon minus the work function or the threshold energy of that particular metal it can vary from metal to metal the energy of the incoming Photon can be represented by H * you know the frequency the threshold energy is going to be Plank's constant times the threshold frequency and of course you can write the equation this way we can replace frequency with the speed of light divided by the wavelength so I like to use the equation in this form so if you know the wavelength of light that is strike in the metal and you know the work function or the threshold energy of the metal you can calculate the kinetic energy of the ejected electron now once you calculate the kinetic energy sometimes you need you may need to calculate the speed of the electron and so you could use this Formula K is equal to 12 MV ^2 the mass of an electron is 911 * 10 -31 kg GRS by the way for those of you who want a list of these formulas if you want to be able to print it out feel free to check out the links in the description section below I'm going to be posting a formula sheet that has all of these formulas and more now sometimes you may need to calculate the maximum wavelength that is needed to free an electron from a metal and that Max wavelength is equal to Plank's constant times the speed of light ID by the threshold energy or the work function now sometimes the work function instead of giving it to you in Jewels you may get it in electron volts and you need to convert it to Jews one electron volt is 1.62 * 1019 jewles so you could use that conversion factor to convert the work function from electron volts to Jews now the next Formula we're going to talk about is De Broly's wavelength to calculate the de brogly wavelength it's equal to the Plank's constant divided by the mass of the object and the speed of the object if you need to calculate the momentum of a particle or even a photon it's simply mass time velocity and you can also use this equation to calculate the momentum Plank's constant divided by the wavelength now sometimes you need to calculate the energy of a photon that is emitted from a hydrogen atom so let's say you have a hydrogen atom and let's say this is the first energy level the second energy level and the third energy level and let's say we have an electron in the third energy level and it falls to the first energy level when an electron falls from a higher energy level to a lower energy level it's going to emit radiation typically in the form of photons so we want to be able to calculate this emitted Photon the energy of the emitted photon is Nega 2178 * 10 to the ne8 Jew * 1/ N Final 2 - 1/ n initial squ by the way for those of you who want to see example problems on how to use this formula feel free to check out the links uh down below this video I'm going to be posting some other YouTube videos that has example problems that show you how to to use these formulas that you're seeing here so for this particular example the electron it went from the n 3 energy level to the nal1 energy level so n i the initial energy level would be three and final the final energy level is one and then once you plug this in you can get the energy of the photon and once you know the energy of the photon you can calculate the frequency using this Formula E H or you can calculate the wavelength by taking the Plank's constant multiplying by the speed of light and dividing it by the energy so once you know the energy you can calculate the frequency of the photon and its wavelength if needed using those two formulas now some other things that you may need to know we talked about the mass of an electron you also need to know the mass of a proton which is 1. 6726 * 10 - 27 kg and the mass of a neutron is 1.67 49 * 10 -27 kg for those of you who want the rest of the notes and formulas for this kind of topic feel free to check out the formula sheet and you can get the formulas that we've discussed in the video today for those of you who prefer just to print it out so I'm going to stop it here and thanks again for watching this video