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प्रश्न
What type of lens is used to correct Astigmatism?
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उत्तर
Cylindrical lens
संबंधित प्रश्न
Name the body part with which the terms myopia and hypermetropia are connected.
Differentiate between myopia and hypermetropia.
What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.
The picture given here shows a person wearing ‘half-moon’ spectacles. What sort of eye-defect do you think he has? Why are these particular spectacles useful to him?
A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of:
(i) 5 cm?
(ii) 25 cm?
(iii) 50 cm?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need?
What is Hypermetropia (far sightedness)?
Differentiate between:
Short-sightedness and Long-sightedness.
Explain the Term: Hypermetropia
What type of lens is used to correct Hypermetropia?
A person is unable to see clearly a poster fixed on a distant wall. He however sees it clearly when standing at a distance of about 2 m from the wall.
- Draw ray diagram to show the formation of image by his eye lens when he is far away from the wall.
- List two possible reasons of this defect of vision.
- Draw ray diagram to show the correction of this defect using appropriate lens.
