## Question

A person can see clearly only up to a distance of 30 cm. He wants to read a book placed at a distance of 50 cm from his eyes. What is the power of the lens he requires for his spectacles?

### Solution

–1.33 D

The person is myopic. This defect is correct by using a concave lens. Putting *u* = –50 cm and *v* = –30 cm in the lens formula fives *f* = –75 cm. Therefore, the power of the lens

= **– 1.33 D**.

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A person with defective eyesight is unable to see objects clearly nearer than 1.5 m. He wants to read a book placed at a distance of 30 cm from his eyes. Find the power of the lens he requires for his spectacles.