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प्रश्न
When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
उत्तर
- Myopia : When a person can see nearby objects clearly but cannot see distant objects distinctly then the person is suffering from myopia. A person with this defect has the far point nearer than infinity. Myopia is also known as near-sightedness.
Myopia eye - Correction of Myopia : Wearing of concave lens diverges the light rays to help the image to be focused on the retina, hence myopia is corrected using the concave lens of suitable focal length.
Correction for Myopia - Hypermetropia: When a person can see distant objects clearly but cannot see nearby objects distinctly, then the person is suffering from hypermetropia. The near point, for the person, is farther away from the normal near point (25 cm). Hypermetropia is also known as far-sightedness.
Hypermetropic eye - Correction of hypermetropia : Wearing a convex lens in front of a hypermetropic eye converges the light rays to help the image to be focused on the retina, hence this defect is corrected using the convex lens of suitable focal length.
Correction of hypermetropia eye
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संबंधित प्रश्न
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.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Name any two defects of vision which can be corrected by using spectacles.
Name the defect of vision which can be corrected by a converging lens. Show clearly by a ray diagram how the lens corrects the defect.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Give two possible reasons for this defect of the eye in human beings.
Rewrite the following table so as to match second and third column with first column.
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Column I
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Column II
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Column III
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(i) Myopia
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Old age problem
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Bifocal lens
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(ii) Presbyopia
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Nearsightedness
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Concave lens.
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Give Technical Term:
The type of lens used to correct myopia is
Assertion: Concave mirrors are used as reflectors in torches, vehicle head lights and in search lights.
Reason: When an object is placed beyond the center of curvature of a concave mirror, the image formed is real and inverted.
A teacher drew the diagram of the heart on the blackboard and told the students to copy it in their notebooks. Mahesh couldn't see the diagram clearly as it appeared blurred to him.
- Name the defect of the eye Mahesh is suffering from.
- Where is the image formed in this defect?
- Mahesh consults an eye doctor and is prescribed suitable lenses to correct the defect. Which type of lens do his spectacles have?
