Question

A professor reads a greeting card received on his 50th birthday with + 2.5D glasses keeping the card 25 cm away. Ten years later, he reads his farewell letter with the same glasses but he has 'to keep the letter 50 cm away. What power of lens should he now use ?

Comments

How can the near point comes out to be positive??? Pls answer

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near point of the eye is with respect to the eye and not with respect to the lens.

Answer 1

On the 50^th birthday, he reads the card at a distance 25cm using a glass of +2.5D. Ten years later, his near point must have changed. 

So after ten years,