Question

$\textbf{What is human eye? \ \textless \ br /\ \textgreater \ \ \textless \ br /\ \textgreater \ What are its various parts? \ \textless \ br /\ \textgreater \ \ \textless \ br /\ \textgreater \ Draw a diagram representing internal structure of human eye. \ \textless \ br /\ \textgreater \ \ \textless \ br /\ \textgreater \ Define each part. \ \textless \ br /\ \textgreater \ \ \textless \ br /\ \textgreater \ Explain working of eye too. }$

Answer 1

#The human eye is roughly spherical in shape with diameter of about 2.3 cm.

#It consists of a convex lens made up of living tissues.

#Hence, human lenses are living organs contrary to the simple optical lenses. 

#The white of the eye is known as the sclera. It is the tough, opaque tissue that protects the outer layer of the eye. 

#Iris is the coloured part of the eye, and the pupil is the black part.

1.

Pupil

Opens and closes in order to regulate and control the amount of light

2.

Iris

Controls light level similar to the aperture of a camera

3.

Sclera

Protective outer coat

4.

Cornea

Thin membrane which provides 67% of the eye’s focusing power

5.

Crystalline lens

Helps to focus light into the retina

6.

Conjunctiva

Covers the outer surface (visible part) of the eye

7.

Aqueous humour

Provides power to the cornea

8.

Vitreous humour

Provides the eye its form and shape

9.

Retina

Captures the light rays focussed by the lens and sends impulses to the brain via optic nerve

10.

Optic nerve

Transmits electrical signals to the brain

11.

Ciliary muscles

Contracts and extends in order to change the lens shape for focusing

Answer 2

$\textbf{The Human Eye }$:

Human eye is the most important organ. It is used to see the beautiful nature and the natural phenomena. The human eye works on the refraction of light through a natural convex lens made of transparent living material and enable us to see things around us.

$\textbf{The main parts of human eye are }$:

Cornea, Iris, Pupil, Ciliary muscles, eye lens, retina and optic nerves.

1. $\textbf{Cornea}$:

It is transparent part of eye and allow the light to enter in the eyes, it is the outermost part of the eye.

2. $\textbf{Iris}$:

It is a circular diaphragm having a hole in it's centre. This hole is called $\textbf{pupil}$. The circular diapragm has muscles and coloured pigments. The colour of an eye depends on the colour of these pigments. The function of iris is to control the amount of light entering the eye through the pupil. The pupil becomes small when bright light falls on the eye but it becomes wide when there is dim light

3. $\textbf{Eye lens }$:

The eye lens is a crystalline double convex lens and made of transparent and flexible tissues. It is behind the pupil and help them by the muscles called ciliary muscles. It focuses the images of objects on the retina of the eye.

4.$\textbf{Ciliary Muscles }$:

These muscles hold the eye lens in position. It controls the focal length of eye lens. When these muscles contracts the focal length of the lens increases when they expands they exerts pressure on the lens and decreases focal length.

5. $\textbf{Retina}$:

It acts as a screen to obtain the image of object. It contains number of cells in the form of rods and cones which are sensitive towards light. These cells convert light energy to into nerve impulses or signals.

6. $\textbf{ Optic Nerves }$:

Optic nerve is found by the nerve fibres coming from the retina. It transfers nerve impulses to the brain.

$\textbf{Working of the eye }$:

When will look towards an object light from the object enters the pupil of the eye and falls on the eyelens. The 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 carried to the brain through the optic nerves.