NTSE Stage 2 SAT 2016 Question Paper

Question : 36 of 100

Marks: +1, -0

A person can see clearly only the objects situated in the range 50 cm to 300 cm. He went to an Optometist who prescribed him a lens of certain power to increase the maximum distance of his vision to infinity, i.e., it corrected the near-sightedness. However, upon using the prescribed lens the person discovered that the near point of his vision has shifted from 50 cm to a distance “d” What is the value of d ?

60 cm
100 cm
40 cm
500 cm

Validate

Solution:

Case : I

\u=-∞

\f=?

Now using formula

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

1/\f=-1/300-0

\f=-300 \cm

Case : II

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

-1/300={-1}/50-1/\u

1/\u={-1}/50+1/300

1/\u=({-6+1}/300)

1/\u=-1/60

\u=-60 \cm

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