 move to the next one start solving this question I'll upload another one these are the last two questions for today okay are you getting 30 second option 3 all of you see angular position is defined as suppose this is the point for which you need to find angular position let's say this is the point this points angular position is this angle fine that that's how you define the angular position of a point on the screen okay now if theta is the angular position do you know that the path difference between these two is nothing but d sine theta okay which can be approximated to d tan theta as well fine so let's say that I mean the path difference between these two is d sine theta okay now intensity has to be 1 4 so intensity formula is what I is equal to 4 I not cos square 5 by 2 okay one fourth of the maximum intensity now maximum intensity is 4 I not so one fourth of that is I not so you can find out the value 5 for which I becomes equal to I not by using this formula okay so you will get cos of 5 by 2 to be equal to plus minus 1 by 2 now plus minus 1 by 2 actually represent one point above and the other similar point below so we'll just focus on the point above so I'll just take the positive value over there so pi by 2 should be equal to what angle pi 5 by 2 will be equal to pi by 3 okay so the phase difference should be equal to 2 pi by 3 fine if phase difference is 2 pi by 3 what will the path difference part difference should be equal to lambda by 2 pi into phase difference that's how you convert between phase difference and path difference right so this will be equal to lambda by 3 fine now d sine theta if you quit that to lambda by 3 you'll get theta is equal to sine inverse of lambda by 3d that's why option 3 is correct over here fine now try out question number 33 all right anyone 33 no one should I solve it okay let me solve it now so I'll just briefly discuss this question probably then I'll leave it after that so that you can also do it your own okay so first of all PC is a wave front the P and C are the points on the same wave okay hence P and C are in phase phase of P is equal to phase of C okay now what happens this point C moves forward get reflected and reaches P okay so between this ray and this ray okay the path difference is CO plus OP and because of hard reflection lambda by 2 this is the path difference okay so always take care of the reflection also when there is a hard reflection lambda by 2 you should add all right now see oh and OP you can find out OP is what this angle is theta okay so this D is given and here it is 90 degree so OP you can write it as D divided by cos of theta is OP okay and once you get OP you have a 90 degree angle here as well you can get CO as well CO is OP cos of 2 theta okay which is D by cos theta into cos of 2 theta cos of 2 theta is cos square theta minus sine square theta okay so you can use all that and then just substitute the value of OP and CO in this particular equation and you need to have a concept of interference over here right so for concept of interference delta x should be at least equal to lambda so you can just put the value over here as lambda and then just simplify it and you will get the answer I'll tell you the correct answer over here 30th the correct answer is this 33rd okay fine so that's it for today from my side so