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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
Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?
List three common refractive defects of vision. Suggest the way of correcting these defects.
The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(d) hypermetropia
The picture given here shows a person wearing 'half-moon' spectacles. What sort of eye-defect do do you think he has? Why are these particular spectacles useful to him?
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
By closing the eyes and gently pressing them by your palms, you may see some specks of brilliant light. How do you get this sensation while there is no light entering your eyes?
What is Hypermetropia (far sightedness)?
Give Reason:
Why do we see clearly in the central region of the retina?
Which of the following statement is correct?
Complete the following table by observing the given figures:
| Figure → |  |
 |
| Points ↓ | ||
| (a) Name of the defect | ______ | ______ |
| (b) Position of the image | ______ | ______ |
| (c) Lens used to correct the defect | ______ | ______ |
