• 4 months ago
Transcript
00:00Hi kids! Today we will learn about the working of human eye. So let's start!
00:09We learned different parts of the eye. Now we will learn how our eyes works.
00:19Our eye is a spherical structure. It has a bulging part in the center of its
00:27front side and it's called cornea. It is a thin, shiny, transparent layer which is
00:35convex in shape and covers the round colored part of the eye which we call as
00:42iris. Light enters the eye through this cornea. The cornea also acts as the
00:53protection wall for the front of the eye. Light then passes through a small
00:59opening called the pupil which is present in the center of the iris.
01:08Iris controls the amount of light that will enter through the pupil. When there is a
01:15bright source of light, iris makes a pupil contract so that less amount of
01:22light enters the eye. And when the light is dim, iris makes a pupil expand or
01:30dilate so that more amount of light enters the eye. Now the light hits the
01:39lens behind the pupil. The lens is convex in shape and is made up of transparent
01:47jelly-like material and it is this lens that focuses the light onto the retina
01:53where the image is formed. The lens changes shape to adjust for close or
02:01distance vision. Ring-shaped ciliary muscles are present around the lens and
02:11these muscles contract or relax to focus varying distant objects. In case of
02:20distant objects, the ciliary muscles relax and the lens becomes thin and more
02:26convex. This enables the lens to focus distant objects and we are able to see
02:33distant objects more clearly. And in case of closer objects, the ciliary muscle
02:40contracts and lens becomes thick and flat. This enables the lens to focus the
02:47near objects on the retina. Retina. The innermost and third layer is called
02:54retina. It is light sensitive and like the screen of camera, retina is made up
03:01of two types of receptor cells, rod cells and cone cells. Rod cells are sensitive
03:08to dim light and don't provide us colored vision. So everything is gray or
03:16black and white in dim light. And cone cells are sensitive to bright light. It's
03:24the cone cells because of which we see colorful things. Now an inverted and tiny,
03:35that is, very small image is formed on the retina of both eyes. And this image
03:44is sent by the cells of the retina to the brain through optic nerve. And this
03:53optic nerve is present in the central region of the retina which is called
03:59macula. And it's our brain that combines the separate images produced by our eyes
04:07and gives us a 3D view. So kids, we learned how do we see or how our eye
04:18works. Now let's revise it all. Light enters the eye through the cornea which
04:25is thin layer in front of the iris, the colored round part of the eye. And light
04:33then passes through the pupil. And pupil is a small opening in the center of the
04:40iris. Iris controls the amount of light that enters the pupil. Iris makes the
04:48pupil expand in case of dim light so that more light enters the eye. And in
04:56case of bright light, iris makes a pupil contract so that less amount of light
05:05enters the eye. Now the light hits the lens and lens that focuses the light on
05:14the innermost layer of the back surface of the eye which is called retina. Iris
05:21muscles help the lens to focus the image on the retina. When an object is at
05:29distance, the iris muscles relax and the lens becomes more convex. And it focuses
05:38the distant object. And when the object is very near, the ciliary muscle
05:44contract and the lens flattens because of which it is able to focus the near
05:52object on the retina. Now let's talk about retina. We have two types of cells
05:59in the retina. Cone cells and rod cells. Cone cells are sensitive to bright light
06:08and give us color vision. And rod cells are for dim light and gives us grayish
06:16or black and white vision. And on this retina, a very tiny inverted image is
06:25formed. Yes, the inverted image. Cone cells and rod cells sends this image
06:35formed on retinas to the brain through optic nerve. And these inverted images
06:43formed on the retinas of both the eyes are combined by the brain and
06:50interpreted. And we see a 3D view. So kids, we have learned how our eye works.
07:00Now you may go ahead and take a quiz to learn more. Bye-bye!