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प्रश्न
Give Reason:
Deficiency of vitamin A causes night blindness.
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उत्तर
Because the visual purple (Rhodopsin) of the rods is not formed in the absence of vitamin A.
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संबंधित प्रश्न
About 45 lac people in the developing countries are suffering from corneal blindness. About 30 lac children below the age of 12 years suffering from this defect can be cured by replacing the defective cornea with the cornea of a donated eye. How and why can students of your age involve themselves to create awareness about this fact among people?
Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.
Where is the near point of a person suffering from hypermetropia (or long-sightedness)?
A man can read the number of a distant but clearly but he finds difficulty in reading a book.
What type of spectacle lens should he use to correct the defect?
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.
Explain with the help of labelled ray-diagram, the defect of vision called hypermetropia, and hot it is corrected by a lens.
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
Select the odd one in the following series:
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot.
Assertion: Myopia is the defect of vision in which a person cannot see distant objects clearly.
Reason: This due to eye-ball being too short.
Have a look at the posture of this girl who is reading a book and answer the questions which follow:
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- Name the problem she is facing.
- What are the two conditions shown in sections A and B of the eye as applicable to her.
- What kind of reading glasses does she need?
 |
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| A | B |
