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Class 10 Science Chapter 11 Revision Notes

Notes
Course

Pedagogy Of General Science (XXII a,b)

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Class X Science vedantu 1

Revision Notes

Class – 10 Science

Chapter 11 - Human eye and colourful world

The front part of the eye is covered with a transparent spherical membrane known as the cornea. Light enters the eye through the cornea. Space present just behind the cornea contains a fluid known as aqueous humour.

Just behind the cornea is a muscular diaphragm, which is dark coloured and is known as the iris which has a small circular opening in the middle called the pupil. The black colour of the pupil is due to no light being reflected from it. The iris is responsible for controlling the amount of light entering the eye by adjusting the size of the pupil.

The lens of our eyes is a convex lens made of a transparent jelly-like proteinaceous material. The eye lens is hard in the middle and becomes soft towards the outer edges. The ciliary muscles hold the eye lens in its position. The ciliary muscles are responsible for changing the curvature and focal length of the eye lens.

The inner back surface of the eyeball is the retina. It is a semi-transparent membrane that is light sensitive and behaves as the screen of a camera. The light-sensitive receptors present in the retina are rods and cone cells. When the light falls on these receptors they are responsible for sending electrical signals to the brain via the optic nerve. The space between the retina and eye lens is filled with vitreous humour.

The light coming from an object enters the eye through the cornea and pupil. The eye lens is responsible for converging these light rays to form a real, inverted and diminished image on the retina. The light-sensitive cell present in the retina gets excited as the light incidents and generates electrical signals. These electric signals are sent to the brain via the optic nerves and the brain interprets these electrical signals in such a manner that we are able to see an image that is erect and is of the same size as that of the object. Accommodation of the eye is said to be the ability of the eye to focus on objects lying at certain distances.

Whereas the range of vision is the distance between the near point and the far point.

Class X Science vedantu 2

Colour vision occurs through cone cells of the retina which are excited only in bright light. You cannot differentiate between red, violet or purple flowers in a garden in moonlight, because of the rod cells function and not of cone cells.

(Source:- vedantu/biology/diagram-of-eye)

Defects of Eye

  1. Colour blindness or colour vision deficiency is a condition in which a person is unable to distinguish between certain colours. The most common cause could be genetic. Cone cells, which are colour sensitive receptors containing single visual pigments which are selective for red, green, and blue light, are present in the normal human eye. Disturbances in colour vision occur when the amount of pigment per cone is either reduced or are absent.

  2. Nyctalopia is an inability of a person to see in relatively low light. It is considered a symptom of several eye diseases. Night blindness could be inborn or can occur due to any injury or malnutrition. Lack of Vitamin A could also play an important role in this. The outer layer of the retina is composed of more rods than cones. The rod cells are responsible for the vision in low light and the reason why loss of side vision often results in night blindness.

    1. Cataract is an opacity in the crystalline lens of the eye. In the early stage of age-related cataract, the crystalline lens power can be increased, causing near-
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Class 10 Science Chapter 11 Revision Notes

Course: Pedagogy Of General Science (XXII a,b)

178 Documents
Students shared 178 documents in this course

University: University of Kota

Was this document helpful?
Class X Science www.vedantu.com 1
Revision Notes
Class – 10 Science
Chapter 11 - Human eye and colourful world
The front part of the eye is covered with a transparent spherical membrane known
as the cornea. Light enters the eye through the cornea. Space present just behind the
cornea contains a fluid known as aqueous humour.
Just behind the cornea is a muscular diaphragm, which is dark coloured and is known
as the iris which has a small circular opening in the middle called the pupil. The
black colour of the pupil is due to no light being reflected from it. The iris is
responsible for controlling the amount of light entering the eye by adjusting the size
of the pupil.
The lens of our eyes is a convex lens made of a transparent jelly-like proteinaceous
material. The eye lens is hard in the middle and becomes soft towards the outer
edges. The ciliary muscles hold the eye lens in its position. The ciliary muscles are
responsible for changing the curvature and focal length of the eye lens.
The inner back surface of the eyeball is the retina. It is a semi-transparent membrane
that is light sensitive and behaves as the screen of a camera. The light-sensitive
receptors present in the retina are rods and cone cells. When the light falls on these
receptors they are responsible for sending electrical signals to the brain via the optic
nerve. The space between the retina and eye lens is filled with vitreous humour.
The light coming from an object enters the eye through the cornea and pupil. The
eye lens is responsible for converging these light rays to form a real, inverted and
diminished image on the retina. The light-sensitive cell present in the retina gets
excited as the light incidents and generates electrical signals. These electric signals
are sent to the brain via the optic nerves and the brain interprets these electrical
signals in such a manner that we are able to see an image that is erect and is of the
same size as that of the object. Accommodation of the eye is said to be the ability of
the eye to focus on objects lying at certain distances.
Whereas the range of vision is the distance between the near point and the far point.

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