Solveeit Logo
Login

Question

Question: A man suffering from myopia can read a book placed at 10 cm distance. For reading the book at a dist...

A man suffering from myopia can read a book placed at 10 cm distance. For reading the book at a distance of 60 cm with relaxed vision, focal length of the lens required will be

A

45 cm

B

– 20 cm

C

– 12 cm

D

30 cm

Answer

– 12 cm

Explanation

Solution

For lens u = want’s to see =−60cm= - 60cm

v = can see =−10cm= - 10cm

∴1f=1v−1u⇒1f=1−10−1(−60)⇒f=−12cm\therefore\frac{1}{f} = \frac{1}{v} - \frac{1}{u} \Rightarrow \frac{1}{f} = \frac{1}{- 10} - \frac{1}{( - 60)} \Rightarrow f = - 12cm