what will be the focal length of eye when ciliary muscles are relaxed
Answers
Eye lens of human eye is a convex lens. Being flexible, the eye lens can change its shape i.e. can become thin or thick to focus light on to the retina. The eye lens are held in position by the suspensory ligaments. One end of the suspensory ligaments is attached to the eye lens and the other end to the ciliary muscles . Ciliary muscles change the thickness of eye lens while focussing.
When the eye is looking at a distant object, then the ciliary muscles of the eye are fully relaxed and these relaxed ciliary mucles of the eye pull the suspensory ligaments attached to the eye lens tightly. The suspensory ligaments in turn pull the eye lens due to which the eye lens gets stretched and becomes thin .Thin eye lens has large focal length.Thus we can say that when the eye is relaxed, the interior lens becomes less rounded and the lens has its maximum focal length for viewing distant objects.
Answer:
The focal length of the eye lens of a normal eye in relaxed position of eye muscles is about 2.4 cm.
Explanation:
When ciliary muscles are relaxed, then the lens becomes thin i.e. the focal length of eye lens increases. The lens has the capacity to increase its focal length in order to view distant objects.
When ciliary muscles are contract, then the lens becomes thicker i.e. the focal length of eye lens decreases . Thus , a sharp image is focused at the retina.
The focal length of a normal eye lens is about 2 cm because distance between eye lens and retina is approximately 2 cm. So, when parallel rays are coming they form image at focus and to make image at retina focal length should be about 2 cm.
Changing the focal length changes the angle of view. The shorter the focal length (e.g. 18 mm), the wider the angle of view and the greater the area captured. The longer the focal length (e.g. 55 mm), the smaller the angle and the larger the subject appears to be.
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