How does the human eye work?

Wednesday, February 12, 2020

How do your eyes convert light into an image that you can see?

Your eyes allow you to see the world around you, in fact, your eyes allow you to watch this video above, but how do your eyes transfer the light energy into impulses that your brain can interpret?

When rays of light bounce off an object like a dog, they first strike your eyes and pass through a structure known as the cornea.
The cornea is a clear membrane, like a window, and covers the front of the eye.
When light passes through the cornea it then passes through a fluid-filled chamber and reaches the pupil. The pupil is an opening through which light enters the eye.
In bright light the pupil is small and in dark light, the pupil opens and is larger.
This is a result of the iris. The iris is a ring of muscle that surrounds the pupil and regulates the amount of light entering the eye.
The iris also gives the eye its color based on the amount of pigment it contains.
When light passes through the pupil it will strike the lens, which is convex in shape.
A convex lens is thicker in the middle compared to the edges.

convex concave lens

Because of the way the lens of the eyes bends the light the image it produces is upside down and reversed. Muscles that are attached to the lens adjusts its shape which allows the light to be clear and in focus.
After passing through the lens the light passes through a jelly-like fluid and reaches the back of the eye onto a surface called the retina. The retina covers the back of your eye and is filled with tiny receptors called rods and cones.

There are over a hundred and thirty million receptor cells. There are two types of receptors, rods, and cones. 
Rod's work best in dim light and allow you to see black and white.
Cones on the other hand cones work better in bright light and enable you to see colors. 
There are three types of cones, red, green, and blue which allows you to see colors around you.

rods and cones of eyes

After the light strikes the rods and cones nerve impulses travel down the optic nerve to the occipital lobe of your brain. At the occipital lobe, the reversed image is turned right-side-up and also combines the images from each eye to make one image.

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