Question

What is human eye and define its parts

Answer 1

Explanation:

human eye is an organ that react to light in many circumstances . the human eye distinguish about 10 million colours

Answer 2

Question

What is Human Eye? Define it's parts.

Asked

Human Eye and Parts

Answer Starts

The Human Eye :-

The human eye is a most important sense organ. It is also a wonderful optical instrument. It is like a camera having a lens on one side and sensitive screen on other side.

Parts of the human eye :-

1. Cornea : It is a transparent spherical membrane in front of the eye. Light enters the eye through the cornea.

2. Iris and Pupil : Iris is a dark-coloured muscular diaphragm which has a small circular opening in its middle. The central circular aperture of iris is called pupil. The pupil appears black because no light is reflected from it. The iris regulates the amount of light entering the eye by adjusting the size of the pupil.

3. Retina : The inside surface of the rear part of eyeball where the light entering the eye is focused is called retina. It acts as a screen for image formation in the eye. The surface of retina consists of about 125 million light sensitive receptors. These receptors are of two types -rods and cones. When light falls on these receptors, they send electrical signals to the brain through optic nerve.

• Cone-shaped - These cells are sensitive to colour.

• Rod-shaped - These cells are sensitive to brightness or darkness or dim light.

It is due to cone-shaped cells that we are able to

differentiate between different colours.

4. Eye lens: Behind the pupil and the iris is the F eye lens. It is a transparent, crystallines structure made up of many concentric layers. It is kept in its position by a strong elastic form called the suspensory ligaments. The eye lens helps to divide the eye into two chambers. The chamber between the cornea and the eye lens is called the anterior chamber and is filled with a fluid called aqueous humour. The back chamber between the eye lens and the retina is called the posterior chamber and is filled with a jelly- like material-called the vitreous humour.

5. Blind spot : There are no rods and cones at the point where optic nerves leave the eye- ball to go the brain. So, if an image is formed in this part of the retina, then no signal is sent to the brain. As a result, the object is not seen. The part of retina is therefore called the blind spot of the eye.

6. Ciliary muscles : These muscles hold the eye lens in position and control the focal length of the eye lens. By contracting and expanding they increase and decrease the focal length of the eye lens. Hence, these muscles have a great role in focussing on the nearby objects as well as far off objects.

Answer Completed

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