Human Eye Class 10 Notes CBSE Science Chapter 11
CBSE NCERT Class 10th Revision Notes Science contains NOTES of Chapter 11 Human Eye topics given in textbook are part of Revision Notes for Class
Science Notes cover an overview of the main given points of every concepts and Topics in the NCERT TextBooks Class 10th Science Important Notes this Chapter Notes includes topic/concepts wise explanations for all the topic provided in the book such as Prism , Human Eye, Near Sightness, Myopia , Cornea and Presbyopia (Old age Hypermetropia
Well prepared Class 10th Science Solutions Notes will guidance students understand the topics ,concepts and themes covered in all the chapters of Ncert Text book of 10th
CBSE Class 10 Chapter-wise Science Notes
Human Eye and It's Parts
Sense organ that helps us to see.
- Located in eye sockets in skull.
- Diameter of Eye is 2.3 cm (Size of eye remains same throughout our whole life)
Parts of Human Eye
1) Cornea –
It is the outermost, transparent part. It provides most of the
refraction of light.
2) Lens –
It is composed of a fibrous, jelly like material. Provides the
focused real and inverted image of the object on the Retina.
This is convex lens that converges light at Retina.
3) Iris –
It is a dark muscular diaphragm that controls the size of the pupil.
4) Pupil –
It is the window of the eye. It is the central aperture in Iris.
It regulates and controls the amount of light entering the eye.
5) Ciliary Muscles –
They hold the lens in position and help in modifying the
curvature of lens.
6) Retina –
It is a delicate membrane having enormous number of light
sensitive cells.
7) Optic Nerve –
It transmits visual information from retina to Brain.
8) Blind Spot –
The point at which the optic nerve leaves the eye.
9) Aqueous Humour –
Between the cornea and eye lens, there is a space filled with transparent liquid is called the aqueous humour which helps the refracted light to be focused on retina. It also provides nutrition to eye.
10) Vitreous Humour –
Space between eye lens and retina is filled with a liquid called Vitreous Humour.
Far Point of Eye –
Maximum distance to which eye can see clearly, is called far point of eye.
- For a normal eye, it’s value is Infinity
Near Point of Eye –
Minimum distance at which an object can be seen most distinctly without any strain is called the least distance of distinct vision.
- For a normal eye, it’s value is 25cm.
Range of Human Vision is from 25 cm to Infinity
Power of Accommodation
It is the ability of eye-lens to adjust its focal length.
- किसी Object को clear देखने के लिए और उस पर focus करने के लिए
Focal Length change करनी होती है
- अगर Object पास में है तो Focal Length कम करनी होगी
- अगर Object दूर है तो Focal Length बढ़ानी होगी
- ये सब करने में Ciliary Muscles help करती है
Case 1) To see far Objects
Ciliary Muscles - Relaxed
Eye Lens – Thin
Focal length - Increase
Case 2) To see near Objects
Ciliary Muscles - Contract
Eye Lens – Thick
Focal length - Decrease
1) Myopia (Near Sightedness) दूर की नज़र कमज़ोर होना
- A myopic person can see nearby objects clearly but cannot
see distant objects clearly.
- Image is formed in front of Retina.
Causes of Myopia
- Excessive curvature of eye lens
- Stretching of eye ball
It is done by using concave lens of appropriate power.
a) In a myopic eye, image of distant object is formed in front
of the retina (not on retina)
b) The far point (F) of a myopic eye is less than infinity.
c) The concave lens placed in front of eye forms a virtual
image of distant object at far point (F) of the myopic eye.
2) Hypermetropia (Far Sightedness) पास की नज़र कमज़ोर होना
- Affected person can see far objects clearly but can’t see
nearby objects clearly.
- The near point of eye moves away.
- Image is formed behind the retina.
Causes of Hypermetropia
- Focal length of eye lens becomes too long.
- Eye ball becomes too small.
It is done by using convex lens of appropriate power.
a) In a hypermetropic eye, image of distant object is formed behind the retina (not on retina)Hypermetropic Eye
The near point (N) of a hypermetropic eye is more than
25cm.
c) Correction of hypermetropia. The convex lens placed in
front of eye forms a real image of near object on Retina.
3) Presbyopia (Old age Hypermetropia)
बुजुर्ग लोगो के पास की नजर खराब हो जाती है, कुछ लोगों को अखबार पढ़ने problem आती है बुढ़ापे में आपने देखा होगा अपने आस पास (grandparents)
It is a defect of vision due to which an old person can’t see
nearby objects clearly due to loss of power of
- The near point of old person having presbyopia becomes
more that 25 cm.
Causes of Presbyopia
- Weakening of Ciliary Muscles.
- Decreasing flexibility of eye lens.
Correction
- It is done by using convex lens of appropriate power.
- Sometimes a person may suffer from both myopia and
hypermetropia. Such people require bifocal lens for
correction.
Advantage of eyes in front of the face
- It gives a wider field of view.
- It provides three-dimensional view.
Prism
It is a pyramidal piece of glass with two triangular bases and three
rectangular faces.
Dispersion of White Light by a Glass Prism –
- The phenomenon of splitting of white light into its 7 colors, when it passes through a prism is called Dispersion.
- This band of seven colors VIBGYOR (Violet, Indigo, Blue, Green,Yellow, Orange, red) is called Spectrum
Ques) Why Dispersion Occurs?
Ans - Light rays of different colors, travel with the same speed in vacuum and air but in any other medium, they travel with different speeds and bend through different angles, which leads to dispersion of light.
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