 n equal to 1, 2 and 3 level for that you need to know velocity as a function of n. We have to derive from where you can derive you have n v r and what else n v square by r with what k times e square by r square you want velocity you want to get rid of r cut one r from here and place it here and then when you divide r will go away fine. So, you will get 1 by v is equal to 1 by v is n h by 2 pi divided by k times e square no something is wrong n v square by r is 1 by 4 pi epsilon naught e square by r I am assuming it e square by r square I am assuming it to be I do not get m v square r is equal to 1 by 4 pi epsilon naught e square and I also know that m v r is equal to n h by 2 pi. So, if you want to eliminate r you can just divide it. So, v will come out to be 1 by 4 pi epsilon naught e square into 2 pi by n h. So, v is equal to e square by 2 epsilon naught h into 1 by n. So, as n increases velocity will go down. Now, you will be able to get right from here it is ok you can put the value of e epsilon naught h you will get the value of v for different times right our next question radius of the innermost electron orbit in hydrogen atom is this 5.3 into 10 raise to power minus 11 this is the radius of the innermost orbit what is the innermost orbit n equal to 1 you need to find radius of n equal to 2 and n equal to 3 n equal to 2 and 3 what is the radius r 1 is given. So, once you get the ratio the ratio will be only in terms of n that that is what I am telling you first get the expression r 1 is proportional to what 1 by n square or n square r is proportional to n square. So, r 1 by r 2 will be n 1 square by n 2 square you getting the same thing r is proportional to n square. So, r if it is proportional to n square you can have r 1 by r 2 equal to what n 1 by n 2 whole square so, from here I can get r 2 is equal to n 2 by n 1 into r 1 n 2 is what 2 1 whole square r 1. So, it is what 4 into r 1 4 times. So, this is 20.6 no sorry 21.2 into 10 is power minus like that you can get for n equal to 3 also for what for n equal to 3 it will be 9 into this right 3 by 1 whole square. So, 9 into that any doubt these are all your NCIT version we are have straight forward and a good thing about these modern physics chapter is this like there is not a big difference between J level and so on. So, you quickly do the FC-Vorma exercises from these chapters and make sure you do not miss a single mark in any kind of exam for these kind of chapters. What are these kind of chapters this entire modern physics then thermodynamics class 11. Then entire classical physics in fact, other than electrostatic they are very very straight forward should not do any marker it is easy to master it that is what I am trying to study. Fine write down next question 12.5 electron volt this much electron beam is used to bombard hydrogen at room temperature what series of wave length will be emitted you need to tell me series with series limer bamer password series of wave length that will be emitted where this will go after absorbing this much which level it will go to how will you find did you get where it will go how can you tell the answer you have to first find out which level it will go to after absorbing this much electron will not be in its ground state it will jump to the other states where it will go to find that first minus 13.6 electron volt is the initial energy e1 e2 will be what minus 13.6 divided by n square electron volt this is energy in nth orbit fine difference in these two energy should be equal to this this is what is absorbed right that is the third postulate those first postulate minus 13.6 by n square minus of minus 13.6 should be equal to 12.5 so what is n divided by 1.5 and then n is the square root of this 13.6 divided by 1.1 roughly how much it is don't guess try to solve let me tell you you guys have lot of lack of practice I can see that there is a huge huge gap between where you should be at this stage and where you are don't waste any time practice lot of questions how much 13.6 divided by 1 by 1 roughly 12 around 12 13.6 divided by 1.1 around 12. what is 26 22 40 12.3 okay this is under root 12.3 now which integer comes close to this 3 and equal to 3 it will not be able to reach 4 so it will come back to 3 and stay there are you getting it so after absorbing this much it will not be able to go to 4 so it will stay at the next possible level it will not go up it will be at n equal to 3 now tell me once it is at n equal to 3 what all series it can emit it can go to n equal to 1 or it can go to n equal to 2 fine so the lowest level tells you which series it is lowest level as in there is a transition between 2 level lower of these 2 levels okay so when it makes a transition from 3 to 2 it is bummer and when 3 to 1 limer and 2 to 1 is also limer so 2 limer series and 1 bummer series ionization energy for hydrogen atom is 13.6 electron volt how much this will be for helium atom what it is for helium how much into z square 54 around let us do this question this is a nucleus of charge z times e so atomic number is z okay e is a charge of electron it requires 47.2 electron volt this much energy is required to excite the electron from second bore orbit to third bore orbit from n equal to 2 to n equal to 3 if you have to go then this much energy is required the ionization energy of hydrogen atom is given actually 13.6 electron volt which you know all anyways for hydrogen atom this is ionization energy question number first what is the value of z and its ionization energy is a second done what is z you did not get the answer energy in the nth orbit for hydrogen like atom will be what 13.6 by n square into z square electron volt energy the second orbit will be 13.6 by 4 z square energy third orbit will be 13.6 divided by 9 z square fine this minus that should be equal to 47.2 isn't it both are electron volt only I do not need to convert in joules so e3 minus e2 should give me 47.2 electron volt that is minus of 13.6 by 9 z square minus minus 0.6 by 4 z square is equal to 47.2 from here you get the value of z all you get ionization energy its energy in first is the ionization model that is the ionization energy once you get the value of z substitute here and put n equal to 1 you get that you get minus of that you need to supply that much energy to make it 0 fine so that is the ionization energy any doubt how will you get potential energy of the electron in the first volts orbit for this potential energy is double of the total energy again and again making the same error potential energy is double of this total energy fine next how will you get angular momentum of the electron in the first more orbit how will you get angular momentum simply it is n h by 2 pi does not matter what is atomic number m v r should be equal to n h by 2 pi okay so for n equal to let us say 2 it will be what 2 times h by 2 pi it will be h by pi only it does not matter what is atomic number angular momentum will be always equal to n h by 2 pi okay fine so that is it for today and we have finished one more chapter from modern physics and you have to do lot of practice lots as in every day at least 60 versions 20 physics 20 chemistry 20 math and you are not asking it sufficient doubts let me tell you you are not ready to realize otherwise you should not realize it after writing the exam you should realize it well before that you are not ready then only you will get prepared okay and I am like I am warning you in a way that your experiences may not be good you will be then I mean I do not want to I do not want you to go to some third grade college or whatever you get or you pay lot of money and then getting to some very very very hard fine so ask lot of doubts be active in a group and follow it up and back it up with lot of practice at home that is it for today you have the knowledge for the test you won't you have the knowledge