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प्रश्न
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.
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उत्तर
The person is suffering from Hypermetropia i.e. far-sightedness.
Hypermetropia is caused due to:
(i) The focal length of the eye lens is too long
(ii) Decrease in the length of the eyeball
This defect can be corrected using convex lens of appropriate focal length.
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संबंधित प्रश्न
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?
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
The near point of a long-sighted person is 50 cm from the eye.
- Can she see clearly an object at:
- a distance of 20 cm?
- at infinity?
- To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?
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?
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?
Explain the Term: Presbyopia
The diagram given below represents the cross-section of the human eye:
(i) Name the parts labeled 1—12.
(ii) What is the function of the part marked ‘10’?
(iii) What would happen if part ‘5’ is damaged or cut?
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.
State reasons for Myopia. With the help of ray diagrams, show the:
- image formation by a myopic eye, and
- correction of myopia using an appropriate lens.
Observe the following diagram and answer questions following it:
- Identify the defect of vision shown.
- List its two causes.
- Name the type of lens used for the correction of this defect.
