 So, the other talk is basically because of your interest in knowing what we are doing in the first year undergraduate lab. So, basically the lecture what I was giving I was instructor earlier, but now I am not. But whatever lecture I used to give to the first year students I have kind of edited and I thought I will show you so that you get I mean I am sure most of the things will be repetition for you, but since you wanted I thought I will show you. Okay, this as I mentioned they do it in the first year, first semester and second semester. So, the contact details some of you wanted so I have written all the details either through mostly you can actually write to us through email. Mr. Anand Raoth was there the other than that day. He was instrumental in setting up the lab not only here in some other places also. Mr. Wag is a actual lab in charge. We can always contact him. He is very helpful anytime you have any difficulty you can always contact us. So, the suppliers you were asking about the suppliers our experiments mostly I mean earlier and some of them now there is this company called Ossova in Ambala. I am sure even if you do a Google you cannot get all the things and as you have seen the other things if you have money if you are rich enough or if you are patient enough to age 50 years like what we did you can try this thing. KTV is a very reputed company global market they have very highly reputed they have an interagent I am not doing an advertisement for them this that I called Alcat they are based in Delhi. So, they do all the things and the advantage is that they can actually get lot of components fabricated locally so that the price actually comes down. So, whatever is possible they will make and they will produce a size accordingly. So, the objectives of this lab are to demonstrate the theoretical concepts of some of the experiments not all 8 experiments right now we are managing. As I mentioned again training for a planning of an experiment and try to get reliable results with the kind of accuracies or error that are there always is the main training that is there. They are also trained to have a training on I mean on this meticulous data collection and that is a thing. The experiments what you have seen I have listed here again we have single slit diffraction basically to verify the uncertainty principle strictly speaking this can be made double slit also and also if you in principle we can use it as an electron thing also if you have an electron source one can do that the usual quantum mechanics double slit experiment to prove the uncertainty principle the idea is this one grating spectrometer of course we do dispersive power LCR circuit we have resonance frequency and Q factor centrifugal force again you have seen basically as a function of mass frequency of rotation and the distance Fresnel bipresum they used to find out the wavelength least diskies to find out the thermal conductivity of a power conductor Helmholtz coil and torque Helmholtz coil is very standard torque is to get the to measure the torque of the on the current loop which acts as a magnetic dipole E by M essentially uses Lorentz force ok. So what I this I do not know whether you are doing it or what we are actually giving them is a very introductory training on error analysis I am let me tell you that this is not a rigorous error analysis if you look at a text when a standard book you will see that we have diluted it but this is a basic training that is given. So suppose they have a graph where it is linear something like this so what they do is they have to plot this so the graph will be something like this and they do what is known as a best fit line and they get the slope for example and they do this is what they were doing earlier before they came to IIT they are done what now they are asked to do is they have to find out associated with the slope what is the error that is there because there is a fluctuation in the data the fluctuation comes because of the random errors and you know the problem of significant digits and accuracy this I am sure you know for example if you find out want to find out the length of this rod using this scale I can only tell that it is between 4 and 5 centimeters anything more if I make a statement it is going to be observed similarly here it is definitely I can tell it is ok it can be 4.6 to 4.7 if I tell that it is because like calculated gives you anything if I tell that the length is 4 point something something something it is it is just ridiculous it does not mean anything. So that is the thing so of course for that one should know this thing this anyway you know the significant digits which are very important in determining the error and the analysis. So the what we are actually asking you to do is only the various errors but we ask them to do only the random error random error means error that is coming and which can be kind of taken care when you do it in repeated times. So basically the random fluctuations of this data that is what is being addressed when they are asked to find out the random error. So I will give you a specific example this one suppose there was a really an offset like this one this is a systematic error we do not ask them to do anything assume that there is no systematic error but even then if I do many measurements like in the case of simple pendulum if I try to find out the time period if I do n number of times I will get different values. So that is the thing that is asked to worry about. Now what we know is we have this things all of you know the average which they have done earlier now this is the standard deviation they we have to define basically we find out with respect to the average what is a deviation the square the mean square that is what is taken here this is taken as the least count if there are only two measurements this becomes the least count if I mean in the random error if there is nothing given the least count divided by 2 is taken as the least the error. This is a main issue the suppose a formula involves of this this kind of expressions the corresponding error the absolute errors f corresponding to this one is delta f they are the ones like this one this is a very simple differential calculus we use this this is not rigorously correct but we just take it as in the first case. So what we do is these are all the fractional errors this is the absolute error what I have to do is they from the mean value what they have been doing earlier also we have this f average assume that we are looking at f quantity f so they know the f average using the formula from the formula of this kind they can find out what is delta f by f by calculation. So if I multiply the 2 I will get delta f so that will allow me to write the result as f plus or minus delta f then but delta f also the calculator will give you a number of digits where do I do that so that is what is done the position of the most significant digit in the error the absolute error that is taken and only up to that limit the main result also will be quoted like for example suppose you are trying to find out the measurement and the lambda measurement the lambda average you got it as 5885 using sodium lamp suppose your calculation you have some formula you do did that differential thing you got delta lambda by lambda as this one your calculator gave me I gave this one. So the delta lambda will be the product of these two again I will get so many digits you see the digits we are getting. So what is done is we take the most significant digit here that is 2 and it is in the 10th position it becomes 20 so the error associated with this is written as 20 and correspondingly by this fellow will also be taken the 10th position it is 8 but the next one is 5 5 or more I take it as the next one I will write as 5890 so it becomes 5890 plus or minus 20 so this is the way we do it for almost all the things just to give an idea where the blunder can happen is this one you are measuring the g the last slide you are measuring the g assume that my measurement due to whatever calculation I got this one suppose these are the delta g values I am getting the absolute error for g after doing this calculation multiplication suppose I am getting this one that means the estimation is very good so that means I can write most significant digit is actually the fourth decimal it is very very high accurate the accurate so I can write my value as 9 again there also the main result also I can go up to fourth decimal so I write it as 9.8326 plus or minus again the fourth decimal suppose it was not that good I will get only this my most significant digit is third decimal correspondingly this also will be truncated to third decimal here it is truncated to second decimal and so on so this is what is told them this is really for this mistake we really penalize them if there is no mercy on it even if they do some other mistake but this part they have to really really do without anything this much they should understand this is something which generally they have been appreciating over generations they have been appreciating as a main training they are getting from this lab I mean I am talking about these things were implemented earlier when we had very crude experiments not these fancy experiments what you have seen now when we had a very old experiments we were implementing it this you can also do that I mean not a difficult thing at all ok so this they should know that if I write 9.8 and 9.80 there is a difference there is a big difference that they should know I think engineering students definitely should know this different the references of course I am here I should acknowledge the first year lab team consists of various many many people over many I should sell generations people have contributed especially professor major who had a big contribution in the development of this manual and so on so after that any anything I mean can write and these all these things I will put in the your movie thank you.