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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?
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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
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.
Which defect of vision can be rectified:
by using a concave lens?
What is the scientific name of
short-sightedness
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
What type of lenses-converging or diverging-would an optician prescribe for her?
A man can read the number of a distant but clearly but he finds difficulty in reading a book.
What type of spectacle lens should he use to correct the defect?
A person suffering from the eye-defect myopia (short-sightedness) can see clearly only up to a distance of 2 metres. What is the nature and power of lens required to rectify this defect?
A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia
The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
(a) myopia
(b) presbyopia
(c) colourblindness
(d) cataract
Which part of the eye is grafted in a needy patient from a donated eye?
Name an old age eye defect. What happens in it?
A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
What eye defect is hypermetropia? Describe with a ray diagram how this defect of vision can be corrected by using an appropriate lens.
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
Differentiate between:
Short-sightedness and Long-sightedness.
Give Technical Term:
The path which responsible for protecting the eye from sweat.
Study the following diagram carefully and then answer the questions that follow. The diagram is depicting a defect of the human eye :
(i) Identify the defect shown in the diagram.
(ii) Give two possible reasons for the above defect.
With respect to human eye explain:
(i) How is the image formed on the retina?
(ii) How is the amount of light entering the eye-controlled?
(iii) What type of lens is used for the correction of ‘Long sight’ defect?
(iv) With the help of a ray, diagram show the defect of the eye and then its correction after the use of a lens.
