Question

A near-sighted man can clearly see object only up-to a distance of 100cm and not beyond this. What is the number of the spectacles lens necessary for the remedy of this defect

Answer 1

Answer:

The distance that the near-sighted man can see clearly is 100 cm, i.e., 1 m

It is seen that for correcting myopia, an object that is placed at an infinite distance must form an image that is 100 cm using the corrective spectacles.

Assume that F was the focal length of the lens, v was the distance of the image and u was the distance at infinity, thus;

1/v – 1/u = 1/f

(1/-1) – (1/ - ∞ ) = 1/f

1/f = -1

Thus, the power of the new spectacles would be -1

Answer 2

Answer:

Explanation:

The power of the lens should be such that the image of an object at infinity is obtained at a distance of 100 cm =1 m by the lens.