 Have you noticed that whenever you are focusing on things that are far away, like this coconut tree in the background, things that are close by appear to be blurred? But if you focus on the things that are close by, like this doll over here, then the background becomes blurred. Why does that happen? It happens because of something called accommodation. Let's see how that works. Here's a schematic of your eyeball. These are the ciliary muscles. And imagine right now your ciliary muscles are relaxed and your eye lens is very thin. So in this case, when you're looking at things that are far away, look, the amount of bending needed to bring these rays to focus on your retina is not much. You don't need a lot of power to bend these rays and to focus these rays. And therefore, when you're looking at things that are far away, your eyes are nicely relaxed. Now let's see what happens when this relaxed eye is looking at things that are close by. So here it is, it's the relaxed eye. When things are close by, look at what happens. What I've made sure is the bending here and the bending here is exactly the same. I have bent these rays by the exact same amount that I've bent over here. What do you notice? Now the rays of light are no longer focused on the retina. Why is that happening? Because when things are close by, the incident rays are no longer parallel. And so if you bend by the same amount, look, it's not enough to focus it on the retina. This is why when your eyes are relaxed, your ciliary muscles are relaxed, your lens has very low power. And therefore, you are able to see things that are far away, they're being focused, but things that are close by are not getting focused because they're not bending enough and therefore getting focused on your retina of the eyes. So how can we focus things that are close by? Well, we need to have more bending power. We need to increase the power of your lens. How to do that? Well, your ciliary muscles can contract, they push and make your lens more spherical. Here you go. See, by pushing, by contracting the ciliary muscles, they're making your lens more spherical and that's how your power increases. Now because the bending power has increased, look, now that your bending power has increased, you will be able to focus things that are close by. But now what happens when you are looking at things that are far away, when your eyes have more power? Well, let's look at it. Your eyes are more powered and now let's see what happens when you are looking at things far away so rays of light will be parallel. Look, I have now put the same bending power over here. Hey, it's bending too much and it's getting focused in front of your eyes. And that's why now the things that are far away will not get focused on the retina. So what's happening is that because your bending power is very high, because your ciliary muscles have contracted, you're able to see things that are close by, but with things that are far away, it appears very blurred. You will not be able to focus on it. And that's exactly what happens over here. Very high power, you're able to see it, but because of the same high power, the rays of light are getting focused in front of the retina and therefore it gets blurred. And what's important is that you don't have to memorize this. Logically, if you think about it, you'll understand it. When you're looking at things far away, you need low power, eyes are relaxed. When you're looking at things that are close by, you need to increase the power of your lens and therefore your eyes are, your ciliary muscles are contracted, your eyes are actually a little stressed. But the last thing is that the closer the object comes, more power you need. But there is a limit to how high your power can go, right? There's a limit to that. For the normal eye, that limit is roughly around 25 centimeters. Not that if you bring the object closer than 25 centimeters, your eyes will get too stressed. You will not be able to increase that power too much. And so this point where your eyes as a limit, they cannot increase the power anymore, is called the near point of your eye. And we usually represent it with D. So for human beings, we usually consider the near point to be around 25 centimeter. It's not exact. It'll depend from people to people. But this means if objects are farther away from 25 centimeters, you can still accommodate. Your eyes can accommodate and you can see it. But if objects are closer than 25 centimeters, then your eyes will not be able to accommodate. It will not be able to increase the power anymore. And that's basically what accommodation is. Ability to change the power, accommodate the power depending upon how far or how close the objects are.