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प्रश्न
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
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उत्तर १
A person with a myopic eye should use a concave lens of focal length 1.2 m so as to restore proper vision.
उत्तर २
The person is able to see nearby objects clearly, but he is unable to see objects beyond 1.2 m. This happens because the image of an object beyond 1.2 m is formed in front of the retina and not at the retina, as shown in the given figure.
To correct this defect of vision, he must use a concave lens. The concave lens will bring the image back to the retina as shown in the given figure.
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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.
List three common refractive defects of vision. Suggest the way of correcting these defects.
the biological/technical terms for the lens of eye losing flexibility resulting in a kind of long-sightedness in middle aged people.
Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.
A man can read the number of a distant but clearly but he finds difficulty in reading a book.
From which defect of the eye is he suffering?
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
Name the type of defect he is suffering from.
Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects 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?
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
What is meant by optical illusion? Give one example.
Enumerate the common defects of vision, their causes and the possible methods of correcting them.
What eye defect is hypermetropia? Describe with a ray diagram how this defect of vision can be corrected by using an appropriate lens.
Have a look at the posture of this woman who is reading a book and answer the questions which follow:
What are the two conditions shown in sections A and B of the eye as applicable to her?
The near point of the eye of a person is 50 cm. Find the nature and power of the corrective lens required by the person to enable him to see clearly the objects placed at 25 cm from the eye?
A person is unable to see objects distinctly placed within 50 cm from his eyes.
(a) Name the defect of vision the person is suffering from and list its two possible causes.
(b) Draw a ray diagram to show the defect in the above case.
(c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm.
(d) Draw a labeled diagram for the correction of the defect in the above case.
Name the common defects of the eye.
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
Due to elongation of _______ and increase in curvature of the eye lens, a person cannot see distant objects clearly.
Write scientific reason.
Nearsightedness, this defect can be corrected by using spectacles with concave lens.
