Question

a person with a defective eye vision is unable to see the objects nearer than 2m. he wants to read a book at a distance of 40 cm.the power of lens he needed in his spectacles is​

Answer 1

Answer:

Explanation:

This person suffers from the defect of hypermetropia.

For him u = -30cm, v = -1.5 m = -150cm

Therefore, focal length of corrective lens to be used by him is

1/f = 1/v- 1/u = 1/-150 - 1/-30 = 4/150 = 37.5cm

The positive sign shows that the lens needed is a convex lens of focal length 37.5 cm.

Hence, power of lens needed

P =1/f = 100/37.5 = 2.67D