 Let's see how to draw ray diagrams for convex lenses. Imagine we have a convex lens of focal length 10 centimeters and there's an object kept at 30 centimeters. I want to know where the image is going to be, what its nature is going to be. How do we figure this out? The first step is to draw a diagram. We'll draw the lenses, we'll draw the focal length. So this focus is at 10 centimeters from the optic center. And then we'll also mark 2f, which is twice the distance, 20 centimeters from here. This means that object which is at 30 centimeters must be beyond 2f in this particular situation. So we'll draw it over here. Now there are three rays that we can draw. The first ray from the top going parallel to the principal axis. This after refraction will go through the principal focus. Because that's what principal focus is. All the parallel rays of light after refraction goes through it. The second ray of light we can draw through the optic center. That's the specialty of the optic center. It goes undeviated. So it will not refract, it will go straight. Now these two rays are enough. But if you want, you can also draw a third ray which is passing through the principal focus. Now after refraction, it will go parallel to the principal axis. This is exactly opposite of the first one. If the incident ray is parallel, the refracted ray goes through the focus. If the incident ray is going through the focus, the refracted ray goes parallel to the principal axis. And now wherever these three meet, that's where your image is going to be. And therefore, you can see you'll have the tip of the object going down, giving you an inverted image. And so our image is between f and 2f, which means it's going to be between 10 centimeters and 20 centimeters. We've also seen that it's inverted, which means it's real image. And you can see the size is smaller. So it's diminished. And the point is, you don't have to remember any of this. You can always draw these ray diagrams and you can figure it out. So let's practice the remaining cases. So here are some other cases. And all the cases I've kept object at different locations. Why don't you pause the video and see if you can draw a couple of ray diagrams and identify where the image is going to be? Why don't you pause and try? All right, I'm going to start with this one. And for all the cases, I'm only going to draw the yellow ray and the blue ray. And we will see we'll be able to get all the information of the image. All right, so here we go. Look, parallel goes through the focus and optic center goes undeviated. Notice where you are getting the image in this case. Oh, we are getting it exactly at 2F. So when the object is at 2F, image is at 2F. And if you look carefully, the sizes are the same, inverted, meaning real image. Okay, let's go over here. Again, same story. I'm going to draw the same two rays. Parallel goes through the focus and the one going through the optic center goes undeviated. See where they meet. They meet beyond 2F, which means when the object is between F and 2F. Notice I'm getting an object which is beyond 2F. It's inverted and it's bigger than the object. So this time I'm getting a real, magnified image. Okay, what if I'm having the object at F? Again, same story. Two rays of light, parallel goes through the focus and the other one goes straight, undevated through the optic center. Notice these two rays are exactly parallel to each other, which means they're not going to meet ever. So you'll get no image in this particular case. When the object is at F, you get no image at all. And in the final case, you have the object in between F and O. Well, again, same thing. You have one ray parallel going through the focus. Another one goes undeviated through the optic center. This time also they don't meet, but they're not parallel. You can see they're diverging. The two rays are going away from each other. And therefore, if I extend them backward, there they meet. This means the rays appear to be coming from here. So we're going to get an enlarged image. But this time it's erect. This means it's a virtual image. You can't capture this on a screen. You get a virtual erect, enlarged image. Okay, finally, let's go to a concave lens. And again, even here, you can try to draw these two rays of light and see where the image is going to be. Why don't you pause and try it yourself first? Okay, this time the parallel ray of light will get refracted not through this focus. But remember, these are diverging lenses. So it'll go diverge away from the principal axis, but it'll appear to be diverging from this focus. That's the key. That's the key difference between these two. And of course, the second ray I can direct it at the optic center just like before, and it'll go undeviated. This will be the same whether you have convex or concave because there's no refraction happening. And now just like this case, you can see these two rays are going away from each other. They're not meeting, but they appear to come from here. See, they're not really meeting. This ray is not really here. It appears to come from here. So they appear to meet, and therefore, we get a virtual erect image over here. And you will find that regardless of where you keep the object, wherever location you keep the object, you'll always find a diminished virtual image between FNO. And that's something that you can try it out yourself. So isn't this amazing whichever lens you're dealing with, wherever the object is, you can figure out everything about the image, where it will be, its size, whether it's real or virtual, all by drawing two rays of light. Amazing, isn't it?