Advertisements
Advertisements
Question
Ciliary muscles of human eye can contract or relax. How does it help in the normal functioning of the eye?
Solution
The ciliary muscles of the human eye can contract or relax the eye lens and help in changing the focal length of the eye lens. Because of this, the eyes can focus the images of nearby as well as distant objects on the retina.
We can understand this by following examples:
(a) When the eye is focussing on a distant object. In this case, the ciliary muscles are completely relaxed. The relaxed muscles tightly pull the suspensory ligaments, which in turn pull the eye lens, because of which the eye lens becomes thin. The thin eye lens has a small converging power, which is sufficient to converge the parallel light rays from the distant object to form an image on the retina.
(b) When the eye is focussing on a nearby object. In this case, the ciliary muscles contract, because of which they cannot pull the suspensory ligaments tightly. As the suspensory ligaments are loose, they stop pulling the eye lens, and therefore the eye lens bulges and becomes thick. The thick eye lens has greater converging power, which helps in converging the diverging light rays from the nearby object to form an image on the retina.
APPEARS IN
RELATED QUESTIONS
What change is made in the eye to enable it to focus on objects situated at different distances? Illustrate your answer with the help of diagrams.
Explain the functions of the following parts of the eye:
(i) cornea
(ii) iris
(iii) pupil
(iv) ciliary muscles
(v) eye-lens
How does the eye change in order to focus on near or distant objects?
(a) The lens moves in or out
(b) The retina moves in or out
(c) The lens becomes thicker or thinner
(d) The pupil gets larger or smaller
Given below is certain structure. Write against them its functional acivity.
retina and ……………………….
Name the respective organs in which the following are located and mention the main function of each:
(i) Iris
(ii) Semicircular canals
Name the following:
The part of the eye responsible for change in the size of the pupil.
Choose the Odd One Out:
Which one of the following statements is NOT correct?
In human eye the part which allows light to enter into the eye is ______.
Match the following:
| Column - I | Column - II | ||
| 1 | Retina | a | pathway of light |
| 2 | Pupil | b |
far point comes closer |
| 3 | Ciliary muscles | c |
near point moves away |
| 4 | Myopia | d | screen of the eye |
| 5 | Hypermetropia | e | power of accommodation |
