Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
(a) Is she short-sighted or long-sighted ?
(b) What type of lenses-converging or diverging-would an optician prescribe for her ?

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Solution

(a) Short-sightedness
(b) Diverging lens

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Q. Your friend can read a book perfectly well but cannot read the writing on the blackboard unless she sits on the front row in class. Is she short-sighted or long-sighted?

Q. 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?
(b) To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?

(a) What is long-sightedness ? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show :
(i) the eye-defect long-sightedness.
(ii) correction of long-sightedness by using a lens.
(b) An eye has a near point distance of 0.75 m. What short of lens in spectacles would be needed to reduce the near point distance to 0.25 m ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ?
(c) An eye has a far point of 2 m. What type of lens in spectacles would be needed to increase the far point to infinity ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ?

Q. Complete the following sentences :
(a) A short-sighted person cannot see .............. objects clearly. Short-sightedness can be corrected by using ............... lenses.
(b) A long-sighted person cannot see ............... objects clearly. Long-sightedness can be corrected by using .............. lenses.

Q. A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
(a) Name the type of defect he is suffering from.
(b) How can this defect by corrected ?

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Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class. (a) Is she short-sighted or long-sighted ? (b) What type of lenses-converging or diverging-would an optician prescribe for her ?

(a) Short-sightedness (b) Diverging lens

Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
(a) Is she short-sighted or long-sighted ?
(b) What type of lenses-converging or diverging-would an optician prescribe for her ?

(a) Short-sightedness
(b) Diverging lens