NTSE Stage 2 SAT 2017 Question Paper

Question : 29 of 100

Marks: +1, -0

To read a poster on a wall, a person with defective vision needs to stand at a distance of 0.4m from the poster. A person with normal vision can read the poster from a distance of 2.0 m. Which one of the following lens may be used to correct the defective vision ?

A concave lens of 0.5 D
A concave lens of 1.0 D
A concave lens of 2.0 D
A convex lens of 2.0 D

Validate

Solution:

the person is myopic and the defective for point is → 0.4 m

\u=-2\m,\v=-0.4 \m

1/\f=1/\v-1/\u

⇒

1/\f={-5+1}/2

={-4}/2=-2

\P=1/\f=-2\D

– ve power indicates concave lens.

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