Notes of Class 10 Science Ch 11 Human Eye and Colourful World | NCERT Class 10

NCERT Class 10 Science Chapter 11

Chapter 11, "Human Eye And The Colourful World," is the second chapter of physics class 10 of NCERT book.In this chapter, we have to study the human eye and its parts, such as the Retina, Iris, Cornea, and Pupil, etc.In this chapter, we will study the basic defects of the human eye such as myopia, hypermetropia, and presbyopia.
In this chapter, we will also study some phenomena related to the light, such as the formation of a rainbow, scattering of light, spectrum, etc.

Notes of Class 10 Science Chapter 11

1. The Human Eye

The human eye is a natural instrument used by humans to see various objects and colors. It is one of the most important sense organs of human beings.

2. Parts of A Human Eye

• Retina = A light-sensitive screen present inside the eye on which images are formed in a healthy eye is called the retina. It contains rods and cones.
• Cornea = A thin membrane that covers the eyes is known as the cornea. It refracts most of the light rays entering the eye.
• Aqueous Humour = A fluid present between the cornea and the eye lens to fill the space between them.
• Eye lens = A convex lens present in the eye made up of transparent and flexible jelly-like material.
• Pupil = Pupil is a hole present in the middle of the iris from which lights enter in the eye. It appears black in color because the light that enters it does not come back.
• Ciliary Muscles = Muscles present in the eyeballs attached with eye lens having the ability to change or modify the shape of the eye lens which changes the focal length.
• Iris = It is the part of the eye which controls the amount of light entering into eye by changing the size of pupil.
• Optical Nerve = After the conversion of the images into electrical signals, these nerves take those electrical signals from eyes to the brain.

3. Accommodation Power

An eye can change the focal length of an eye lens by contracting or relaxing ciliary muscles to get a clear view of either nearby or far distant objects.

4. Colour Blindness

Some people have this defect because they do not have some cone cells that detect various colors due to some genetic disorder.

5. Myopia(Near Sightedness)

It is a kind of defect of an eye in which a person can see near objects clearly but unable to see far objects.

Myopia is due to =

• The decrease in the focal length of the eye lens.
• Elongation of the eyeball.

6. Hyper myopia(Far Sightedness)

It is a kind of defect of an eye in which a person can see distant objects clearly but unable to see nearby objects.

Hypermetropia is due to =

• Increase in focal length of the eye lens.
• Shortening of the eyeball.

7.Presbyopia

It is a kind of defect of the eye which happens due to aging.

It happens due to =

• Decreased flexibility of eye lens.
• Weakened ciliary muscles.

8. Astigmatism

It is a kind of eye's defect in which a person can not focus simultaneously on horizontal and vertical lines.

9. Cataract

A defect of the eye due to the growth of the membrane on the eye lens. This decreases the vision of an eye or even make a person blind. It can only be corrected through surgery.

10. Dispersion of White Light By Glass Prism

It is the phenomena of segregation or separation of white light into its 7 constituent lights. The bend of these 7 colors is called the spectrum.

11. Composition of White Light

White light is made up of 7 colors - Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

12. Monochromatic Light

It is a type of light that contains a single color or wavelength. For example = Sodium Light.

13. Polychromatic Light

It is a type of light that contains more than two colors or wavelengths. For example = White Light.

14. Recombination of White Light

The phenomenon of recombining the dispersed light by just placing a prism inverted in front of dispersed light to recombine the light. This phenomenon is found by Newton.

15. Formation of Rainbow

This is the same phenomenon of dispersion of light by small rain droplets in the atmosphere which acts like small prisms and disperse the white light into its constituent 7 colors forming a rainbow.

16. Scattering of Light

According to Rayleigh's law of scattering the amt of scattered light alpha / (wavelength)2. So that the wavelength of violet, blue, and indigo is lesser as compared to the rest of the colors. So the sky appears blue.

17. Total Internal Reflection

The bouncing back of light of ray of light when it tends to enter from denser to rarer medium with the angle of incidence greater than the critical angle.

The critical angle is the incidence angle by which after refraction light bends at an angle of 90.

Conclusion

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