Human eye class 10th chapter 11

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Here you get the complete information about the Human eye class 10th their function and refraction through prism.

Eye:- A human eye is sensitive part and sense organ of human body which is help to see the whole beautiful world or any object . The shape of our eye is spherical and its diameter is 2.3 cm. When light comes to our eyes the senses of eye cell detect it and send the information in our brain. It transfer the information of object like its colour, depth, movement, shape and other features.

All the information cover from the ncert book Human eye class 10th .

Structure of human eye

Human eye
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Human Eye parts function and its work

when any refracted light ray entering into eyes its first contact with outer surface of eye called cornea

Parts of human eye :- sclera, cornea, iris, pupil, lens, retina, optic nerves, ciliary muscles, optic nerve , cones and rods

lets discuss about all parts :-

Sclera:-Its a outer part of eye which is help to protect our eye, its also known as protective layer ,A white colour part covering the surface of eye.

Cornea:-When refracted light rays reach to our eye surface its first contact with the cornea Its a transparent part of Sclera. Light enter through the cornea.

Retina :- Its consist lots of nerve cells . It convert the information of object through the image form in lens into the electrical impulses and electrical impulses transfer through the optic nerves to brain.

Aqueous humour :- A fluid which fills the space between the cornea and lens .

Eye lens :- It is made up with a transparent and jelly like material control by ciliary muscles .

Iris :- The dark part of eyes is called Iris a muscular and ring like structure found in behind the cornea. Its indicate the colour of your eyes, its help to adjust the exposures.

Pupil:- Pupil is a center part of iris and its control the amount of light enter in our eyes its focused to the retina. Its appear blacks because lights did not come back from it.

Ciliary Muscles :- The muscles tissue which control the movement of lens and pupil which are important part of vision ,There are three muscles in group ciliary, dilatator pupillae , and sphincter pupillae.

Optic nerve :- optic nerve the information of image into brain in form of electric signals There are two type of optic nerve : :cons and rods

Cons:-It is a nerve cells which is sensitive towards the bright light .Its help to centre vision.

Rods:- It is a optic nerve cells which is more sensitive towards the dim light. Its help in peripheral vision.

Peripheral vision :- Its also called side vision, The ability of see any object outside the line of direction.

Human Eye parts and its function class 10th

In the upper paragraph you study about the Human eye now time to study about their function from chapter 11 Human eye class for 10th

Human eye parts Their functions
1. Sclera Its protect the outer surface of eye
2. CorneaA thin membrane which provide 67% of focusing power
3. Aqueous humourGive power to cornea
4. vitreous humourFills the space between retina and lens
5. Eye lens Focus the light into retina
6. IrisIts control the level of light like camera
7.PupilOpen and close to regulate the amount of light
8. Ciliary muscles Help to change the lens shape according to focusing
9. Optic nerveTransmit the electrical impulses to the brain
10.Retinacapture the light rays and transmit to brain via optic nerve
11.Conjuctive Cover the visible outer surface of eye
Human eye chapter 11 class 10th

Work of pupils

Lets explain with example:- Now you all are sitting in a room and watching a movie all lights of rooms are off and continuously watching a movie for 2 or 3 hours , Then you go to the outside you can’t see any thing outside for some time how it would be possible. Here the pupil provide the variable Aperture control by iris. Aperture is similar to camera shutter.

when light is bright pupil contracts and less amount of light enters in eye

When light is dim pupil expands and more light enters in eye

Pupil completely open when iris relaxed

Persistence of vision of eye :- Time of sensation of an object continuously stay in the eye. Time = 1/16 of a second

Power of Accommodation :- The ability of eye lens to adjust focal length with help of ciliary muscles.

Ciliary muscle functions

When muscle is relaxedWhen muscle is contact
1. lens become thin lens become thick
2.increase the focal lengthdecrease the focal length
3.Enable us to see far objectsEnable us to see near objects
Human eye chapter 11 class 10th

To see a clear strain free object the minimum distance of object is 25 cm

The farthest point of eye is infinity

Defect of eye and their correction

Cataract :- The image cannot be seen because the eye lens become milky and cloudy. In this situation the vision of eye completely or partially loss.

Treatment/correction :- cataract surgery, removal of extra growth cataract

Myopia :- Its also called near sightedness in this case a person could not see the object which is far from him but they can able to see nearby object.

Reason behind :- When the curvature of eye lens increases it decrease the focal length , the increase of eye ball (elongation)

Treatment/ Correction :- by using of a concave lens of appropriate power

Hypermetropia :- Its also called as far sightedness in this case a person can able to see far nearby object but cannot see the object which is distant or far from them .

Reason behind :- when the eye lens become thin and increase in focal length, Eye ball become small

Treatment/ Correction :- by using of a convex lens of appropriate power

Presbyopia :- When we become old our eye muscles decrease their flexibility and become weak in this we can’t able to see distance and nearby object . People can suffer both the problem myopia and hypermetropia .

Reason behind :- weaken of muscle of eye and loss of flexibility of eye ball

Treatment/ Correction :- by using of bifocal lens of appropriate power

Bifocal lens :- Its a lens which consist both concave and convex lens upper portion of lens consist concave and lower portion consist convex lens

Refraction of light :- When light rays passes through a medium and get diverted and change their path from it called refraction ,Refraction is due to the different volume or densities of medium where light rays pass.

Prism :- It is 3d object with two triangular bases and three rectangular lateral surfaces, all are same size and shape ,Transparent.

Their surfaces is incline to each other and the angle between them is called the Angle of prism

What is human eye ? chapter 11 class 10th

Refraction of light through prism

Refraction of light through a prism :- when a incident ray come to the prism it refracted the ray called as refraction ray. Light travelled through rarer medium to denser medium bends towards normal,

Glass is denser then air , when the light ray fall on the surface of prism, its bend towards the normal. As a result the emergent light is parallel to the incident ray .

Angle of prism:- the angle between to lateral surfaces of prism

Angle of Deviation:– the angle between the deviation of incident

Human eye chapter 11 class 10th

Dispersion of light

Dispersion of white light:- When a white light passes through a glass prism it splitting into seven different colour ,the splitting of light is called as dispersion of light .The colours are , Violet, Indigo, Blue, Green, Yellow, Orange and Red.

For remember the sequence called VIBGYOR, all colour combination is also known as spectrum , all colour bends at different different angle with the respect of their incident angle. Red light bends more and violet light bends least

Composition of light: White light have seven colours ., violet, indigo, blue, green, yellow, orange and red.

Monochromatic light: Light consist single colour or wavelength is called monochromatic light, example; sodium light.

Polychromatic light: Light consist more than two colours or wavelengths is called polychromatic light, example; white light.

Recombination of white light: Newton found that when an inverted prism is placed in the path of dispersed light then after passing through the prism, they recombine to form white light.

Newton discovered

The first who discovered or observe the spectrum of sunlight with help of glass prism. He tried to split more light from spectrum with the help of another glass prism but he was failed but he repeated same but now he inverted one glass prism with the respect of another and what he see. he saw that all spectrum light get emerged and again converted into white light when it passed through the inverted prism. then he concluded the sunlight is made up with seven colour.

Natural phenomenon and how they happens

Human eye chapter 11 class 10th
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Rainbow: A natural phenomenon where sunlight splitted into a spectrum due to dispersion of sunlight by small droplets of water present in atmosphere.

Formation of the rainbow: The Droplets act like small prism. They refract and disperse the light. Due to the dispersion of light and internal reflection, different colours reach the observer’s eye.
Red colour appears on top and violet at the bottom of rainbow.
A rainbow is always formed in a direction opposite to that of Sun.
– Refraction and dispersion take place.
– Internal reflection takes place.
– Refraction and dispersion take place.

Atmospheric Refraction: The refraction caused by the atmosphere of earth (different layer of air with different densities ) called Atmospheric Refreaction.

Appearance of Star Position: Position of star we see is different from the actual position of star its due to atmospheric refraction.
every layer of earth is different temperature and densities so it refracted the light comes from the star into varities.
Distant star act as point source of light. When the starlight enter the Earth’s atmosphere,

it continuously refracted , due to this changing refractive index i.e. from Rarer to denser. It bends towards the normal.
The apparent position of the star is different from actual position. The star appear higher than its actual position.

Twinkling of Star: It is also caused by the atmospheric refraction. Distant star act like a point source of light. the light beam of star keeps deviating from its path, the apparent position of star keeps on changing because the condition of earth’s atmosphere always change .
Hence, the amount of light enters our eyes fluctuate sometimes bright and sometime dim. This is the “Twinkling effect of star”.

Are planet do twinkling ?

Planets are closer to the earth and they are not a source of light, instead of they reflact low intensity light reaching them, they are close to us so their refraction is low . the size of planets looks more bigger then star. This reason are behind were planet do not twinkling.

Why sunrise see advanced and sunset is delayed ?

Because of atmospheric refraction The sun is visible to us 2 min before the actual sunrise and about 2 min after the actual sunset

Scattering of light: According to the Rayleigh’ Law of Scattering, the amount of scattered light ∝ 1λ4 (λ = wavelength)
Scattering of light decreases with increase in wavelength.

Tyndall Effect: When a light beam strikes, the minor particle of earth’s atmosphere like particles of dust and molecule of air ,the beam of light become visible. The process of scattering of light by the colloidal particle gives rise to Tyndall Effect.
Example :- When sunlight passes through a canopy of a dense forest.
The colour of scattering light is depend on size of scattering particles

very small particles scattered the blue colour shorter wavelength

large particles scatter long wavelength colour like red

very large particles scatter the white light

Cloud appear white:- the size of water droplets is very large hence it scatter the white light equally so the cloud visible white

Colour of sky is blue :- the particles of air and other particle present in atmosphere is smaller then the wavelength of visible light. The blue wavelength is shorter then the red so its scattered the most

Colour of Sunrise and Sunset:

during the sunset and sunrise, colour of the sun and sky appear red. When sunset and sunrise, the sun is near to horizon of earth , and therefore, the sunlight has to travel longer distance in atmosphere. Due to this, most of the 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.

Why the danger signal or sign is made of red colour?
Red colour scatter less in small particles .of fog and smoke, Red light have larger wavelength and distance also so wee can easily see the red light

Sun appears white at noon :- when at noon the sun is appear in our forehead and sunlight travel at shortest distance through the atmosphere, the sun appear the white and little of blue and violet colour is scattered.

What happen when there is no any atmospheric refraction :- Scattering of light didn’t happens and sky become dark .

The chapter is now ended check the post what is metal and non metals

What is human eye

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