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प्रश्न
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.
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उत्तर
(a) The defect of the vision is hypermetropia
Hypermetropia is caused due to:
(i) reduction in the curvature of the lens
(ii) a decrease in the size of the eyeball
(b) Ray diagram:
(c) The corrective lens used for this defect is a convex lens.
Given that the near point of the eye is at 50 cm. The convex lens should form the image of the object placed at the distance 25 cm on the near point of the defective eye.
v = −50 cm
u = −25 cm
`1/"f" = 1/"v"-1/"u"`
⇒ `1/"f"=1/((-50))-1/((-25))=1/50`
Power,`"P"=100/50=+2"D"`
(d) Ray diagram showing the correction of the defect:
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संबंधित प्रश्न
List three common refractive defects of vision. Suggest the way of correcting these defects.
Name any two defects of vision which can be corrected by using spectacles.
Explain the Term: Astigmatism
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.
What are the causes of ‘Myopia’?
Myopia and hypermetropia can be corrected by:
Name the following:
Two kinds of accomodations.
