Human Eye And Colourful World Class 10

In this article you will learn about human eye and colourful world for class 10 and other govt job exam like NTPC // SSC // SSC CGL // All Govt exam. Human Eye And Colourful World Class 10

Eye

Humans have a pair of eyes situated in the sockets of the skull called orbits. The eye ball is mainly spherical in structure.

A human eye has the following main parts .

Cornea ::-

It is the transparent spherical membrane covering the front of the eye. Light enters the eye through this membrane Most of the refraction of light rays entering the eye occurs at the outer surface of the cornea.

Lens ::-

It is the central part of the eye that facilitates the image formation.

Iris ::-

It is dark muscular diaphragm between the cornea and the lens. It controls the size of the pupil. It is the colour of the iris that we call colour of the eye.

Pupil ::-

It is a small hole between the iris through which light enters the eye. In dim light, it opens up completely due to contraction of iris muscles, but in bright light it becomes very small due to relaxation of iris muscles.

Ciliary Muscles ::-

They hold the lens in position and help in modifying the curvature of the lens. Human Eye And Colourful World Class 10

Retina ::-

It is the light-sensitive surface of eye on which the image is formed it hind light-sensitive cells rods and cones. Rod cells respond to the intensity of light and cones respond to the illumination. There number is around 125 million. Number of rod cells is greater than number of cone cells. These cells generate signals which are transmitted to the brain through optical nerves. Human Eye And Colourful World Class 10

Optic Nerves ::-

It transmits visual information from the retina to the brain.

Sclera ::-

It is an opaque, fibrous, protective, outer layer of an eye containing collagen and elastic fibre. It is also known as white of the eye.

Blind Spot ::-

It is the point at which the optic nerves leave the eye. It contains no rods and cones, so an image formed at this point is not sent to the brain. Human Eye And Colourful World Class 10

Age ( Years )	Least Distance Of Distinct Vision
10	18 cm
20	25 cm
40	50 cm
60	200 cm or more

Aqueous Humour

Behind the cornea, we have a space filled with a transparent liquid called the aqueous humour and behind this there is a crystalline lens, which helps to refract light to be focused on retina and maintains intraocular pressure.

Vitreous Humour

The space between eye lens and retina is filled with another liquid called – vitreous humour.

Iris regulates the amount of light entering through the eye by adjusting the size of the pupil.
The pupil appears black, because no light is reflected from it.
The eyeball is nearly spherical in shape with a diameter of 2.3 cm.

Mechanism of Vision

The process of vision take place in the following steps

The light rays in visible wavelength focuss on retina through cornea and lens generate impulse in rods and cones.
Human eyes are composed of opsin (protein) and retinal (aldehyde of vitamin-A). Light induces dissociation of retinal from opsin resulting changes in the structure of opsin. This cause change in membrane permeability.
Consequently, the potential difference generated in the photoreceptor cells. Human Eye And Colourful World Class 10
This produces a signal that generates an action potential in ganglion cells through bipolar cells.
The action potential or impulses are transmitted by the optic nerves to the visual cortex area of the brain, where the neural impulses are analysed. Human Eye And Colourful World Class 10
The image formed on the retina is recognised based on earlier memory and experience. Human Eye And Colourful World Class 10

It is impossible to sneeze with your eyes open.
Babies eyes donot produce tears until the baby is approximately six to eight weeks old.
All babies are colourblind when they are born.
Men are able to read fine print better than women.
Shark cornea has been used in eye surgery due to its similarity with human cornea.
Birds possess sharper vision than humans and they can see ultraviolet frequencies too. The reasons being bird retina do not contain blood vessels which prevent light scattering, they possess extra cone cells and the number of rod cells is almost more than double in them which help them to see at night (e.g., owl).