All About The 'HUMAN EYE'

 The Human Eye

      The human eye is the most important organ of human body. It is used to see the beautiful nature and the natural phenomena. The human eye is shown in figure 

                                            

1. Cornea. Cornea is the outermost part of the eye. It is transparent part of eye and allows the light to enter in the eye.

2. Iris. It is circular dark diaphragm having a hole in its center. This hole is called pupil. The circular dark diaphragm has muscles and color pigments. The color of an eye depends upon the color of these pigments. The function of iris is to control the size of the pupil. On the other hand, pupil controls and regulates the light entering the eye. The pupil becomes small when bright light falls on the eye. However, it becomes wide when there is dim light. 

3. Lens. The eye lens is a crystalline double convex lens and made of transparent and flexible tissue. It is behind the pupil and held by the muscles called ciliary muscles. It focuses the images of objects on the retina of the eye. 

4. Ciliary muscles. These muscles hold the eye lens in position. Ciliary muscles controls the focal length of the eye lens. When these muscles contracts, then the lens become thick and the focal length of the lens decreases. On the other hand, when ciliary muscles are relaxed, then the lens becomes thin and focal length of the lens increases.

5. Retina. It acts as a light-sensitive screen to obtain the image of the object. It contains number of cells in the form of 'rods' and 'cones' which are sensitive to light. These cells converts light energy into electrical impulses or signals.

6. Optic nerve. Optic nerve is formed by the nerve fibers coming from the retina. It carries nerve or electrical impulses or signals to the brain. The brain finally interprets the signal. 

                                             

    Working of the eye

When we look towards an object, light from the enters the pupil of the eye and falls on the lens. The eye lens forms a real and inverted image on the retina of the eye. The retina of the eye contains special cells in the shape of rods and cones. These cells convert light energy into electrical signals. These electrical signals are carries to the brain through optic nerves. The brain finally interprets the signals and hence we see the object. 

      Visual impairment means that the eye does not work properly. Visual impairment occurs when any of the part of an eye involved in the transmission of light like cornea, pupil, eye lens, vetreous humour or the part of eye responsible for carrying electrical impulses to the brain like optic nerve is damaged. 

Facts-

 Human eye is just like a camera.

 Rod shaped cells respond to the brightness or intensity of light. On the other hand, cone shaped cells  respond to the color of light.

 Bee can see ultra-violet light but human eye cannot see U.V. light. 

 Color Blindness. A person of normal vision is said to suffer from color blindness if he is unable to  distinguish between different colors.