 Okay, friends. So here is another question from Ray optics. Let's see how we can proceed here. So if you read the question, it basically asks for the lateral shift if light passes through, you know, a plate, let's say you have a plate like this. Okay, so if you have a plate like this, we need to find out basically that if light is incident at some angle. Okay, so what will happen? It will first bend towards the normal assuming the refractive index of the slab is more than outside and then it will try to bend away from the normal like this. Okay, so basically this first ray is parallel to ray number 3. Okay, but then there is a shift. So if you draw this line and extend it further, there's a shift. Okay, which is equal to this distance. So basically this question asked for what is this distance? Okay, so let us try to see how we can proceed here. So we can say that this is angle of incident psi. Okay, and this angle is angle of refraction. Okay, so this is angle of refraction and if I extend this line a little bit like this, okay, then I can also say that this distance is the thickness of the plate. Let's say this thickness is T, okay, which is given over here as root 2 centimeter. Okay, so if I say that this is point A and second point of refraction is B, now what you can get here is, you know, this is i, this is r, okay, and this angle is also r. Okay, so this angle, since this is r, you can get the value of AB. Okay, AB will be equal to what? AB will be equal to T divided by cos of r. Okay, now why I have done this, why I have found out the distance AB is because I need to find out perpendicular distance between these two parallel lines. Okay, now in order to get perpendicular distance between these two lines, I need to first drop up perpendicular. Okay, so this is the perpendicular and I need to find out, let's say AC, which is perpendicular distance between the two parallel lines. Right, so AC, if you notice here, you will find that AC will be equal to AB into sin of this angle. Okay, let's say that angle is theta. Okay, AB sin of theta. Now theta is what angle? If you look carefully, theta is nothing but i minus r. Okay, so this angle is i minus r because this complete angle is i. Okay, so we can say that AC is T sin of i minus r divided by cos of r. Okay, so if I know all the angles and the thickness of the plate, I will get the deviation, how much that light will suffer. Okay, so now let us see, here we have angle of incidence i given. Okay, now in order to find r, I have Snell's law and effective index, isn't it? So I'll just try to do that. So 1 into sin of 45 degrees should be equal to root 2 into sin of r. Okay, so sin of 45 is what? 1 by root 2. So sin of r will come out to be 1 by 2. Okay, so from this particular equation, you'll get angle of refraction to be equal to 30 degree. Okay, and i is equal to 45 degrees. Then what else? Thickness is also given, which is root 2 centimeters. Okay, so just substitute here all these values and you will get how much light will deviate from it, like how much the lateral shift is for the emergent ray compared to what is the incident ray. Okay, so like this you have to do this particular question.