Name: Primary Colours of Light
Uploaded: 2019-07-19
Duration: 5 min 33 s
Description: Did you know that certain colours are more important than the others? Also, certain colours can be derived using the others! This video explains why.

Question

Explain the structure and functioning of human eye. How are we able to see nearby as well as distant objects?

Accepted Answer

The structure and functioning of the human eye are as given below:

Cornea:- Cornea is transparent. It is responsible for most of the refraction of light rays towards the retina.

Iris:- Iris is a dark, circular, muscular diaphragm behind the cornea. It gives the eye its colour. It also controls the pupil size and thus controls the amount of light entering the eye.

Pupil:- Pupil is surrounded by the iris. It regulates and controls the amount of light entering the eye.

Retina:- The retina is the innermost layer of the eye. It contains an outer pigmented layer and an inner nervous layer which contains the photoreceptors (rods and cones). Cone cells are coned shaped and rod cells are rod-shaped.

Optic nerve:- The optic nerve connects the eye to the brain. The nerve fibres carry impulses from the retina to the visual cortex.

Eye lens:- The eye lens is made up of fibrous, jelly-like material. It is transparent and has a biconvex structure. It forms an inverted real image of the object on the retina and also separates the aqueous and the vitreous humour.

Vitreous humour:- Vitreous humour is clear, semi-solid that supporting the eyeball.

The eye lens forms an inverted real image of the object on the retina. It sends image-electric signals to the brain via the optic nerves. The brain reconstructs an erect image of objects and makes us see as they are.

The curvature of the eye lens can be modified to some extent by the ciliary muscles. The change in the curvature of the eye lens can thus change its focal length. When the muscles are relaxed, the lens becomes thin. Thus, its focal length increases. This enables us to see distant objects clearly. When we are looking at objects closer to the eye, the ciliary muscles contract. This increases the curvature of the eye lens. The eye lens then becomes thicker. Consequently, the focal length of the eye lens decreases. This enables us to see nearby objects clearly.

Rajesh Singh, Indu Gupta and, Sikha Sharma Solutions for Chapter: The Human Eye and the Colourful World, Exercise 3: Long Answer Type Questions

Rajesh Singh Science Solutions for Exercise - Rajesh Singh, Indu Gupta and, Sikha Sharma Solutions for Chapter: The Human Eye and the Colourful World, Exercise 3: Long Answer Type Questions

Questions from Rajesh Singh, Indu Gupta and, Sikha Sharma Solutions for Chapter: The Human Eye and the Colourful World, Exercise 3: Long Answer Type Questions with Hints & Solutions

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