(3) The retina has a large number of light sensitive cells. (2) The eye-lens is a convex lens, so it converges the light rays and produces a real and inverted image of the object on the retina. (1) When we look at an object, then light rays coming from the object enter the pupil of the eye and fall on the eye-lens. The eyelids also shut out light when not required. (8) The eyes also have eyelids which prevent any object from entering the eyes. (7) The space between cornea and eye-lens is filled with a viscous liquid called ‘ aqueous humour and the space between eye-lens and retina is filled with another liquid called vitreous humour. The optic nerve carries the image formed on retina to the brain in the form of electrical signals. The eye-lens focusses the image of an object on the retina. The retina is behind the eye-lens, at the back part of the eye. (6) The retina is a screen on which the image is formed in the eye. On the other hand, a glass convex lens has a fixed thickness due to which its focal length (or converging power) is also fixed, and cannot be changed. The eye-lens is a flexible convex lens whose thickness and hence focal length (or converging power) can be changed by the action of ciliary muscles. The focal length (and hence converging power) of the eye-lens is controlled by ciliary muscles. The ciliary muscles can change the focal length (and hence converging power) of the eye-lens according to the requirements of the eye to see distant objects or nearby objects. (5) The ciliary muscles can change the curvature of eye-lens and make it thin or thick according to the need of the eye. The eye-lens is held in position by ciliary muscles whose one side is attached to the eye-lens and the other side is attached to the eye-ball. The eye-lens is actually a living lens because it is made up of transparent living cells which allow light to pass through them. The eye-lens is a convex lens made of a transparent and flexible material like jelly. The iris is actually that part of the eye which gives the eye its distinctive colour. Iris controls the amount of light entering the eye by adjusting the size of pupil. Pupil appears like a dark spot in the centre of iris because no light is reflected from it. The iris has a hole at its centre which is called pupil. The main function of cornea is to protect the eye but it also helps in focussing some light (by its converging action). The light coming from an object enters the eye through cornea. It is made of a transparent substance and it is bulging out. (2) The front part of eye is called cornea. The outer coat of the eye is tough so that it can protect the interior of the eye from damage during an accident. The main parts of the human eye are : Cornea, Iris, Pupil, Ciliary muscles, Eye lens (which is a flexible convex lens), Retina and Optic nerve. The eye enables us to see the various objects around us. 8 Visually Challenged Persons Can Read and Write.5 Range of Vision of a Normal Human Eye.Question 15 What is meant by least distance of distinct vision? Question 14 What is the range of vision of normal human eye? Question 13 What is the function of retina, iris, ciliary muscles, eye-lens, cornea? Question 12 What is blind spot in the eye? Question 11 Name few food items which contain Vitamin A? Question 10 How you can take care of your eyes? Question 9 What is meant by persistence of vision? Question 8 What is cataract? How can the vision of a person having cataract be restored? Question 7 What is Hypermetropia? How is it caused and corrected? Question 6 What is myopia? How is it caused and corrected? Question 5 What are rods and cones in the retina of our eye? Question 4 How does the eye lens differ form the ordinary convex lens made of glass?` Question 3 Why we cannot see our surrounding clearly when we enter a darkened cinema hall from bright sunshine but our vision improves after some time? Question 2 How does eye adjust itself to deal with light of varying intensity? Question 1 What is night blindness? What causes night blindness?
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