A professor reads a greeting card received on his 50th birthday with + 2.5 D 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?

A far sighted person has his near point 50 cm. Find the power of lens he should use to see at 25 cm clearly.

A far sighted person has his near point 50 cm. Find the power of lens he should use to see at 25 cm, clearly.

A certain person has a minimum distance of distinct vision of 150cm. He wishes to read at a distance of 25cm. What focal length glasses should he use?

A certain person has a "minimum distance of distinct vision of "150cm" . He wishes to read at a distance of "25cm" .What " focal length glasses should he use?

The distance of distinct vision of a person is 50 cm . He wants to read a book placed at 25 cm . What should be the focal length of the spectacles ?

(a) A 40 -year-old professor requires eyeglasses with lenses of 2D power to read a book at 25cm . What is his near point? (b) After 10 years he finds that while wearing same specks he must hold the book 40cm from his eyes. What is his near point now, what power lens does he require now to read a book again at 25cm ?

The distance of distinct vision of a person is 50 cm. He wants to read a book placed at 25 cm. What should be the focal length of the spectacles ?

A magnifying glass of focal length 10 cms is used to read letters of thickness 0.5 mm held 8 cm away from the lens. Calculate the image size. How big will the letters appear? Can you read the lettersif held 5 cms away from the lens? If yes what size would they appear. If No, why not.