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प्रश्न
What type of lens is used to correct Astigmatism?
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उत्तर
Cylindrical lens
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संबंधित प्रश्न
A student is unable to see clearly the words written on the blackboard placed at a distance of approximately 4 m from him. Name the defect of vision the boy is suffering from. Explain the method of correcting this defect.
Draw ray diagram for the:-
(i) defect of vision and also
(ii) for its correction.
The near point of a long-sighted person is 50 cm from the eye.
(a) Can she see clearly an object at:
(i) a distance of 20 cm?
(ii) at infinity?
Name the following:
The eye defect caused due to shortening of the eye ball from front to back.
Given alongside is a diagram depicting a defect of the human eye. Study the same and then answer the questions that follow:
(i) Identify the defect.
(ii) Name the parts labelled 1, 2 and 3.
(iii) Give labelled two possible reasons for this eye defect.
(iv) Draw a labelled diagram to show how the above mentioned defect is rectified.
Give Reason:
Why do we see clearly in the central region of the retina?
Give Reason:
Deficiency of vitamin A causes night blindness.
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
Explain the Term: Hypermetropia
Write scientific reason.
Nearsightedness, this defect can be corrected by using spectacles with concave 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.
