Astigmatism is corrected using
(a) cylindrical lens (b) plano-convex lens
(c) plano-concave lens (d) convex lens
1 Answers
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A spherical mirror and a thin spherical lens have each a focal length of −15 cm. The mirror and the lens are likely to be
By convention, the focal length of a concave mirror and a concave lens are taken as negative. Hence, both the spherical mirror and the thin spherical lens are concave in...
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A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power
(b) – 0.5 D. is the correct option.
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Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of –50 cm.
Hint — P = 1/f where f is in metre. Its unit is Dioptre. Lens is convex in the first case and concave in the second case. Power is equal...
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A convex lens forms a real and inverted image of a needle at a distance of 50 cm from the lens.
Given, Distance of image, v = + 50 cm Distanceofobject, u=? Since the image is real, inverted and of the same size of the object, so object should be placed at the...
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A doctor has prescribed a corrective lens of power + 1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
Given P=+ 1.5D As P=1/f (in metre) , Focal length, f =1/P=1/1.5=0.667m=66.7cm As power of prescribed lens is positive, the lens is converging (or convex) lens.
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State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.
(a) Cutting a log of wood into pieces is a chemical change. (False) (b) Formation of manure from leaves is a physical change. (False) (c) Iron pipes coated with zinc do not...
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What is Kyphosis? What are the reasons or causes of Kyphosis? Can it be corrected with the help of exercise programme?
Kyphosis Kyphosis implies an increase or exaggeration of a backward or posterior curve or a decrease or reversal of a forward curve. It is also called round upper back. Depression of...
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Which defect of the eye can be corrected by using a cylindrical lens?
Astigmatisrn.
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What is astigmatism? What causes astigmatism? How is astigmatism corrected?
In this defect, a person cannot focus on both horizontal as well as vertical lines at the same time. So he can see the objects clearly only in one plane.This...
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Some definitions are given below which can be corrected by changing one word. Correct them.
(a) change “above” with “below” (b) change “evaporation” with “seeping” (c) change “vapour” with “water”
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