Human eye and the Colourful World Notes
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| Human Eye And Colourful World |
Human Eye and It's Parts
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| Parts Of Human eye |
2.Aqueous Humor:-It is water like consistency and it maintains pressure Balance.
3.Iris:-It is muscular diaphragm controls size of Pupil.
4.Pupil:-It regulates the amount of light entering inside the eye.
5.Crytaline Lens:-It refracts the light and foucus the image on ratina.
6.Ciliary Muscles:-They adjust the focal length of lens.
7.Vitreous Humor:-It is Honey Like Consistency.It maintains spherical shape of eye.
8.Retina:-It is photoreceptor screen where image is formed.It has two types of Cells.
(i)ROD:-It sense intensity of Light.
(ii)CONE:-It sense Colour.
9.Optic Nerve:-It connects with brain and convert the optical signal to Electrical Signal.
POWER OF ACCOMODATION
The ability of the eye lens to adjust it's focal length as the distance is called Power of Accommodation.
Ciliary Muscles holds the crystalline lens.Crystalline lens foucus image on ratina.Cilliary Muscles Holds and Release the Crystalline lens as the Direction.
Defects in Eye:Myopia(Near-sightedness)
It is kind of defect in the human eye due to which a person can see near object clearly but he cannot see the distant objects clearly.Myopia is due to
i)Excessive Curvature of Eye lens
ii)Elongation of eyeball.
Hypermetropia(Far-Sightedness)
It is a kind of defect to which a person can see distant objects properly but cannot see the nearby objects clearly.It happens due to
i)Decrease in the Power of Eye Lens i.e, increase in focal length of eye lens.
ii)Shortening of eyeball
Presbyopia(Old Age Hypermetropia)
It is a kind of defect in human eye which occurs due to ageing.It happens due to following reasons
i)Decrease in flexibility of eye Lens.
ii)Gradual Weakening of ciliary Muscles in this a person may suffering from both myopia and hypermetropia.
Dispersion of Light Through Prism
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| Dispersion of Light through Prism |
The Phenomenon of Splitting of white light into its seven constituent colours when it passes through a glass prism is called dispersion of white light.The various colours seen are Violet,Indigo,Blue,Green,Yellow,Orange and Red.The sequence of Colours remembers as VIBGYOR.The band of Seven colours is Called the Spectrum.
Deviation in violet colour is most so wavelength of Violet Colour is Least.Similarly Deviation in Red colour Is Least so Wavelength of Red Colour is Most.
How Rainbow Is Formed?
Rainbow 🌈
The water droplets act like small prism.They refract and disperse the incident Sunlight,then reflect it internally refract it again,when it comes out of the raindrop.Due to the dispersion of light and internal reflection different colours reach the observers eye.
Read Colours appears on the top and violet at the bottom of rainbow.
A Rainbow is always formed in a direction opposite to that of Sun.
Atmospheric Refraction
The refraction of light caused by the Earth's atmosphere Having air layers varying optical densities)is called Atmospheric Refraction.
Why do start twinkle?
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| Twinkling of Stars |
It is also due to Atmospheric Refraction.Distant Start act like a point source of light.As the Beam of starlight keeps deviating from its path the apparent position of Star keeps on changing because physical conditon of Earth's Atmosphere is not stationary.Hence,the amount of light enters our eye fluctuate sometimes bright and dim.This is Twinkling effect of Star.
Advanced Sunrise & Delayed Sunset
Actual Sunrise happens when the sun is below the horizon in the morning.The rary of light from the Sun below the Horizon reach our Eyes because of Refraction of Light.Similary the sun can be seen about few minutes after the actual sunset.Thus the duration of day time will increase by 4Minutes.
Scattering Of Light
This happens because light is Absorbed by the particles in the form of Energy.Thw the Particles flect and emit the light again in all directions.This Phenomenon is known as Scattering of Light
For Examples
- The blue colours of the sky colour of water in deep sea,the reddening of the Sun at Sunrise and the Sunset are some of the wonderful phenomenon we are Familiar with.
- The path of a Beam of Light passing through a true solution is not visible.However its path becomes visible through a colloidal solution is relatively larger.
Why does the Sky appear blue at Day Light
The molecules of air and other fine particles in the atmosphere have size smaller than wavelength of visible.these are more effective in scattering of lights of shorter wavelength at the blue end that the light of longer wavelength at the red end. When Sunlight passes through the atmosphere the fine particles in air scatter the blue colour (shorter wavelength) more strongly than red.The Scattered blue light enters our eyes.If the earth has no atmosphere,there would not have been any scattering.Then,sky would have looked dark.
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| Dark Sky |
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| Blue Sky |
Why Sky Appears red at the time of Sunset and Sunrise?
During Sunset and Sunrise the Sun is near to Horizon and Therefore the Sunlight has to travel larger distance in atmosphere.Due to this,most of blue light(Shorter Wavelength) is Scattered away by the particles.The light of longer Wavelength (Red Colour) reaches our eye.This is why sun appear red in Colour.
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| Red Sky |
Tyndall Effect in Sodium ThioSulphate Solution
When a Beam of Light Strikes,the minute particle of Earth's atmosphere,suspended particles of dust and molecules or air the path of beam become visible.The phenomenon of scattering of light by the colloidal particles gives rise to Tyndall Effect.It can be observed when Sunlight passes through a canopy of a dense forest.the colour of the scattered light depends on the size of scattering particles.
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| Scattering of Sunlight |
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| Faraday Tyndall Effect |
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