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प्रश्न
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
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उत्तर १
While reading a book, the lens is more convex or rounded due to contraction of ciliary muscles because the book is usually read from a short distance. When we raise our head and look at a distant object, the ciliary muscles relax to build the tension on the suspensory ligament so that they can stretch the lens. This change in the curvature of the lens makes us focus on distant object.
उत्तर २
The lens is adjusted through accommodation to focus on a distant object while reading. This is a full description:
- Near Vision (Reading a Book):
- Reading causes ciliary muscle contractions in the eyes.
- When the ciliary muscles contract, the suspensory ligaments that support the lens slacken.
- This enables the lens to become more convex or rounded.
- Transition to Distant Vision (Raising Your Head):
- Your ciliary muscles relax when you elevate your head to focus on a distant object.
- Suspensory ligaments pull and flatten the lens.
- The ciliary muscles relax, and the suspensory ligaments strain on the lens.
- Accommodation Power of the Eye:
- Accommodation refers to the process of adjusting focus by modifying the lens shape.
- The eye's accommodation power relies heavily on the ciliary muscles.
- The eye's capacity to concentrate clearly at diverse distances is vital for adapting to various visual tasks.
The ciliary muscles alter the lens shape dynamically, making it convex for near vision and flat for distant vision. The eye's ability to focus clearly at varied distances is due to the process of accommodation.
संबंधित प्रश्न
Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?
Millions of people in the developing countries of the world are suffering from corneal blindness. These persons can be cured by replacing the defective cornea with the cornea of a donated eye. A charitable society of your city has organised a campaign in your neighbourhood in order to create awareness about this fact. If you are asked to participate in this mission, how would you contribute in this noble cause?
(i) State the objective of organising such campaigns.
(ii) List two arguments which you would give to motivate the people to donate their eyes after death.
(iii) List two values which are developed in the persons who actively participate and contribute in such programmes.
A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.
What is the scientific name of
long-sightedness?
Name one defect of vision (or eye) which cannot be corrected by any type of spectacle lenses.
What is Hypermetropia (far sightedness)?
Select the odd one in the following series:
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot.
Anuja cannot see the blackboard writing but she can see nearby things.
(a) What is the eye defect she is suffering from?
(b) State the possible reason for her defect.
(c) How is it corrected
Explain the Term: Hypermetropia
A person is unable to see clearly a poster fixed on a distant wall. He however sees it clearly when standing at a distance of about 2 m from the wall.
- Draw ray diagram to show the formation of image by his eye lens when he is far away from the wall.
- List two possible reasons of this defect of vision.
- Draw ray diagram to show the correction of this defect using appropriate lens.
