So once the light hits our cornea, it basically bends and it enters the lens through our pupil. Now, once it enters the lens, from physics we know that the lens is a convex lens and a convex lens basically diverges the rays of light. So the lens of the eye is a convex lens that is used for fine tuning and focusing the light rays onto a special region at the back of the eye known as our retina. Now, just like the pupil can basically be controlled, the length can also be controlled by a set of smooth muscles known as the ciliary muscles found inside our section shown here. Now, the ciliary muscles are controlled by the autonomic system. And basically, by changing the shape of our lens, we're essentially changing the focal length of that lens.