all formula in class 10 lesson human eye and colorful world
according to the syllabus of 2022
Answers
Answer:
Human Eye: working of human eye, Persistence of vision, Power of accommodation of human eye, Defects of vision.
The Human Eye: It is a natural optical instrument which is used to see the objects by human beings. It is like a camera which has a lens and screen system.
Structure of the Human Eye
Human Eye and Colourful World Class 10 Notes Science Chapter 11 1
The various parts of eye and their functions :
Retina: It is a light sensitive screen inside the eye on which image is formed. It contains rods and cones.
Cornea: It is a thin membrane which covers the eye trail. It acts like a lens which refracts the light entering the eye.
Aqueous humour: It is fluid which fills the space between cornea and eye lens.
Eye lens: It is a convex lens made of transparent and flexible jelly like material. Its curvature can be adjusted with the help of ciliary muscles.
Pupil: It is a hole in the middle of iris through which light enters the eye. It appears black because light falling on it goes into the eye and does not come back.
Ciliary muscles: These are the muscles which are attached to eye lens and can modify the shape of eye lens which leads to the variation in focal lengths.
Iris: It controls the amount of light entering the eye by changing the size of the pupil.
Optical nerve: These are the nerves which take the image to the brain in the form of electrical signals.
The human eye is roughly spherical in shape with a 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 following table lists the main parts of the human eye and their respective functions.
S.No. Human Eye Part Functions
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 Protects the outer coat.
4. Cornea A thin membrane which provides 67% of the eye’s focusing power.
5. Crystalline lens Helps to focus light into the retina.
6. Conjunctive Covers the outer surface (visible part) of the eye.
7. Aqueous humour Provides power to the cornea.
8. Vitreous humour Provides the eye with its form and shape.
9. Retina Captures the light rays focussed by the lens and sends impulses to the brain via the 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.
How Pupil Works?
For Example, You would have observed that when you come out of the cinema hall after watching the movie in the bright sunlight, your eyes get closed. And when you entered the hall from the bright light, you won’t be able to see and after some time you would be able to see. Here, the pupil of an eye provides a variable aperture, whose size is controlled by iris.
(a) When the light is bright: Iris contracts the pupil, so that less light enters the eye.
(b) When the light is dim: Iris expands the pupil, so that more light enters the eye.