Question

A long sighted man cannot see clear objects that are less than 120cm away what is the type of focal length of lens required to make him read a book 30cm away ?​

Answer 1

Answer:

He needs a convex lens of focal length of 40cm......

Explanation:

u=30cm, v=-120cm

1/f=1/u + 1/v

1/f=1/30 - 1/120

1/f=4-1/120

1/f=3/120

3f=120

f=120/3

.: f = 40 cm...