Question

Help Me Friends please
explain the parts of human eye

Answer 1

parts of  human eye:

1.iris -in humans and most mammals and birds the iris is a thin, circular structure in the eye,responsible for the diameter and size of the pupil and thus the amount of light reaching the retina.the iris determines the color of the eye.

2.pupil- the pupil is a hole located in the center of the iris of the eye that allows light to strike the retina.It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.

3. retina-The retina is the sensory membrane that lines the inner surface of the back of the eyeball. It's composed of several layers, including one that contains specialized cells called photo receptors.

4.cornea-The cornea is the clear front surface of the eye. It lies directly in front of the iris and pupil, and it allows light to enter the eye.

5.optic nerve-The optic nerve is located in the back of the eye. It is also called the second cranial nerve.The job of the optic nerve is to transfer visual information from the retina to the vision centers of the brain via electrical impulses.

6.lens-The lens is a transparent structure behind the iris, the colored part of the eye. The lens bends light rays so that they form a clear image at the back of the eye – on the retina. As the lens is elastic, it can change shape, getting fatter to focus close objects and thinner for distant objects.

7. sclera-The sclera, also known as the white of the eye, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some elastic fiber.

8.vitreous humor-The vitreous body lies at the back of the eye, between the lens and the retina. The vitreous body is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates. It is often referred to as the vitreous humor or simply "the vitreous".

9. ciliary muscles-Ciliary muscle: A circular muscle that relaxes or tightens the zonules to enable the lens to change shape for focusing. The zonules are fibers that hold the lens suspended in position and enable it to change shape during accommodation.

Answer 2

$\huge{human \: eye}$
✨ The human eye is nearly spherical in shape with diameter of about 2.5cm. Light enters through a transparent curved from surface. This is known as the Cornea of eye. It is whitish in colour. It's main function is to act as a protective layers for the eye.


✨ The space behind it is filled with a liquid called acqueous humour.

✨ The Cornea is a dark coloured muscular diaphragm called iris.

✨ The lens of the eye forms a real, inverted image of the object on the inner coat of the eye. This screen of the eye is called retina.

$\bold{how \: do \: we \: see \: colours}$

✨We know that our retina has a large number of light sensitive cells having shapes of rods and cones. The rod shaped cells respond to the amount of incident light energy, i.e to different degrees of brightness and darkness. In dim light, the rods are sensitive but the cones are not. They respond mainly to the colours of the incident light. They become active in bright light only and then enable us to make colour perception possible. The cones are generally sensitive to red, green blue light to different extents.✨

$\huge{range \: of \: vision}$
⏺Our eyes are such a wonderful optical instrument that they can see distant as well as nearby objects with almost the same clarity. This becomes possibly because of the ability of our eye lens to adjust its shape and focal length with the help of the ciliary muscles.

⏹ When these muscles are relaxed , the focal length is about 2.5cm and object at infinity are in sharp focus on the retina. When an object is brought closer to the eye, the focal length of eye lens becomes shorter. The eye does this because the lens-image distance, for the eye, has to remain constant and equal to the size of the eye ball. This special property of the human eye is called it's power is accommodation.

⏺ The minimum distance , at which object can see most distinctly is called the least distance of distinct vision or near point of eye. For a young adult with normal eyes, this normal neat point distance equals 25cm. This distance increases with age due to decreasing effectiveness of ciliary muscles.

$\bold{hope \: it \: helps \: you}$
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