Accommodation of an Eye


 
 
Concept Explanation
 

Accommodation of an Eye

Accommodation :

 It is the process by which eye changes the focal length of the eye lens with the help of cilliary muscles such that a sharp image is always formed on the retina. Light rays enter the eye first through the cornea, which is the clear dome at the front of the eye. The light then progresses through the pupil, the circular opening in the center of the iris and then to the crystalline lens, which is located just behind the pupil. The light rays were first bend by the cornea, and  then further by the crystalline lens.

How the Eye Adjusts for Objects at Different Distances: 

For clear vision, sharp images of objects has to be formed on the retina. Since the distance of the retina from the eye-lens is fixed, so the distance of the image is fixed. However, we need to see objects that are at different distances from the eye.

To form clear and sharp images of both at the same distance from the lens, the focal length of the eye-lens has to change. The cilliary muscles are used change the focal length of the eye-lens. When we are looking at a distant object (usually farther than 6 m), the cilliary muscles are in their most relaxed state. Then the focal length of the eye-lens is such that rays coming from the distant object are focused on the retina, and we see the object clearly.The minimum distance, at which objects can be seen most distinctly without strain,is called the least distance of distinct vision  and the farthest point upto which the eye can see object clearly is called as the  far point of the eye. It is infinity for the normal eye

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Sample Questions
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Question : 1

Power of accommodation of eye implies__________

Right Option : C
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Question : 2

In old age, people generally have to wear spectacles for reading and writing because ____________________ .

Right Option : B
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Question : 3

When the eye is focused on an object very far away the local length of the eye-lens is ___________________.

Right Option : A
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