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The Human Eye and the Colourful World

Introduction

Let us discuss the concept, the human eye, and the colourful world in brief. The human eye is an organ that allows vision and reacts to light. The Rod and Cone cells present in the retina allow vision and conscious light perception, including the perception of depth and colour differentiation. The human eye is possibly capable of detecting a single photon and can differentiate between about 10 million colours. The eye is the sensory nervous system part.


The human eye's non-image-forming photosensitive ganglion cells in the retina similar to other mammals' eyes, receive light signals which affect the adjustment of the size of the pupil, suppression, and entrainment of the body clock and regulation of the hormone melatonin.


The eye is one of the five major senses in the human body. It is truly a magical organ, and without this, the world will be dark. The eye comes under the sensory nervous system and can recognize up to 10 million different colours. It helps us gain our vision with the help of the Rod and Cone cells.


Let us talk about the structure of the eyes as it is somewhat a complex organ.

  • It is in the shape of a spherical ball.

  • The socket of the eye holds it. 

  • Two layers named Scleroid and Choroid cover it.


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It is a naturally occurring optical body element as we know that we have a pair of eyes, and its function is to allow us to notice. Without that part, the whole world would have been a dark place for us.


Structure of a Human Eye

  • It is a circular or spherical ball with a small bulge on the front

  • It is located in the socket of the eye

  • It has two layers that cover it which are, scleroid and choroid


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Function of Scleroid

Scleroid is the outermost covering layer that consists of white fibres, and its functionality is to protect all parts of the eye.


Function of Choroid

The choroid is a grey membrane that is attached to a choroid from the inner side. Its functionality is to darken the eye from the inside. So, no internal reflection takes place.


Eye Defects

Let us have a look at a few eye defects that occur very generally for more human beings.

Myopia (Short-Sightedness)


In this defect, a person is unable to see far objects clearly whereas can see the nearby objects. This is because the ciliary muscles don't relax, and the lens doesn't elongate properly because of which the focal length does not properly increase. Resultantly no clear image is formed.


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Defect on Eyes: Eyeball, as being too elongated, the converging lens power is also too high. Because of this, the image is formed in front of the retina, and the brain cannot identify it. It can be overcome using spectacles containing a concave lens that diverges the rays first. Then, our (the human) eye lens can converge them on the retina properly.


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Hypermetropia (Long-Sightedness)

In this defect, a person is unable to see nearby objects but can see far off objects. This is because the ciliary muscles don't contract properly, the lens doesn't become thick and short because of which the focal length doesn't decrease. Resultantly, the image formed is not clear, and the brain can't identify it.


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Defect on Eye

Eyeballs being converging power and too short of the lens is too low. Due to this, the image forms behind the retina. It can be overcome by using spectacles containing a convex lens that increases the ciliary power of the eye lens. So that it can converge rays on the retina properly.


Refraction through Prism

Prism: Prism is a piece of any transparent material or a piece of glass bonded by triangular and three rectangular surfaces. The rectangular surfaces are referred to as refracting surfaces. Where the angle between two refracting surfaces is called the angle of the prism or refracting angle.


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The line along where the two refracting surfaces meet is referred to as refracting the edge. Any of the prism sections that are perpendicular to the refracting edge is called the principal section of the edge.


The refraction via glass prism and glass slab differences can be given below.


The emergent ray lies parallel to the incident ray in the slab but considering a prism, the emergent ray won't be parallel to the incident ray due to the opposite faces of the prism eye are not parallel to one other.


Dispersion

It is the phenomenon of splitting light into seven colours. When light (Sunlight or bulb light) is allowed to pass via glass prism, it splits into seven colours. It happens because we know white light is a combination of seven colours and on entering the prism, each colour gets refracted by different angles because of which different colour (spectrum) is obtained on the screen.


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The obtained colours are Red, Orange, Yellow, Green, Blue, Indigo, Violet.


The human eye, the colourful world, can be obtained by the below explained colours, which are a part of the spectrum.

  • In red colour, wavelength decreases and frequency increases

  • Red colour - Least Deviated

  • Violet colour- Maximum Deviated

  • All seven colours can recombine to produce white light


An application of dispersion is the formation of a Rainbow.


Rainbow

It is an example of dispersion (Spectrum produced by the dispersion of sunlight). "It is formed by the dispersion of white sunlight by the raindrops that are present in the atmosphere.” Each and every raindrop acts as a tiny glass prism. A Rainbow is always formed opposite the sun. White light enters these raindrops. Different coloured rays are refracted through different angles where the rainbow is formed thus.



Scleroid and Choroid

The scleroid is the first layer from the outside that covers the eye. It protects all parts of the eye. The choroid is the second layer of the eye and is filled with a grey membrane. It helps in darkening the eyes from the inside so that there is no reflection. 


Myopia Vs Hypermetropia

Myopia is a defect that doesn't let people see far placed objects. It doesn't affect near objects. There are certain scientific reasons for this. Though it can be cured by wearing spectacles and it has all the possible treatments with the doctors. This generally happens because the ciliary muscles don't relax, which doesn't let our eyes form a clear image. Whereas Hypermetropia is a  defect that is just the opposite of Myopia. Here, the ciliary muscle doesn't contract properly. In this, a person is unable to see nearer objects clearly whereas has no problem in seeing the faraway objects. This also has all the cures in today's world and wearing spectacles can help. 


What is Prism?

Prism is a piece of any glass material or a piece of glass fortified by three-sided and three rectangular surfaces. The rectangular surfaces are alluded to as refracting surfaces. Where the point between two refracting surfaces is known as the point of the prism or refracting point. The concept of a rainbow is also a part of the study of Prism. Every single raindrop goes about as a small prism. The Rainbow is constantly framed against the sun. White light enters these raindrops. Distinctive hued beams are refracted through various points and hence a beautiful rainbow is formed.


 When we do the prism concept, the colours achieved are: 

  • Red - Wavelength decreases and frequency increases. It is also the least deviated colour. 

  • Violet - It is the maximum deviated colour, unlike red. 

  • If we combine all seven colours, we will form white colour.

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