Explain the structure and working of a human eye.
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Answer:
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Explanation:
Structure of Human Eye
A human eye is roughly 2.3 cm in diameter and is almost a spherical ball filled with some fluid.
It consists of the following parts:
Sclera:
It is the outer covering, a protective tough white layer called the sclera (white part of the eye).
Cornea:
The front transparent part of the sclera is called cornea.
Light enters the eye through the cornea.
Iris:
A dark muscular tissue and ring-like structure behind the cornea are known as the iris.
The colour of iris actually indicates the colour of the eye.
The iris also helps regulate or adjust exposure by adjusting the iris.
Pupil:
A small opening in the iris is known as a pupil.
Its size is controlled by the help of iris.
It controls the amount of light that enters the eye.
Lens:
Behind the pupil, there is a transparent structure called a lens.
By the action of ciliary muscles, it changes its shape to focus light on the retina.
It becomes thinner to focus distant objects and becomes thicker to focus nearby objects.
Retina:
It is a light-sensitive layer that consists of numerous nerve cells.
It converts images formed by the lens into electrical impulses.
These electrical impulses are then transmitted to the brain through optic nerves.
Optic nerves:
Optic nerves are of two types.
These include cones and rods.
Cones:
Cones are the nerve cells that are more sensitive to bright light.
They help in detailed central and colour vision.
Rods:
Rods are the optic nerve cells that are more sensitive to dim lights.
They help in peripheral vision.
At the junction of the optic nerve and retina, there are no sensory nerve cells.
So no vision is possible at that point and is known as a blind spot.
An eye also consists of six muscles.
It includes the medial rectus, lateral rectus, superior rectus, inferior rectus, inferior oblique, and superior oblique.
The basic function of these muscles is to provide different tensions and torques that further control the movement of the eye.
Function of the Human Eye
As we mentioned earlier that the eye of a human being is like a camera.
Much like the electronic device, the human eye also focuses and lets in light to produce images.
So basically, light rays that are deflected from or by distant objects land on the retina after they pass through various mediums like the cornea, crystalline lens, aqueous humour, the lens, and vitreous humour.
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Explanation:
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