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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
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.
Name the body part with which the terms myopia and hypermetropia are connected.
Differentiate between myopia and hypermetropia.
Observer the following diagram and answer the questions.
a) Which eye defect is shown in this diagram?
b) What are the possible reasons for this eye defect?
c) How this defect is corrected, write it in brief?
The diagram alongside represents a section of a mammalian eye.
(i) Label the parts 1 to 5 of the diagram.
(ii) State the function of the parts labelled 4 and 5.
(iii) With the help of a diagram show the short sightedness.
Have a look at the posture of this woman who is reading a book and answer the questions which follow:
What kind of looking glasses she needs?
Explain the Term: Presbyopia
Explain the Term: Astigmatism
Observe the figure whether it is correct or not and explain the phenomenon.
