Question

A person uses spectacles of power +1.0 D , find the type of lens and focal length if lens used

in spectacles​

Answer 1

Answer:

The power of the spectacles used by the myopic person, P=−1 D

The focal length of the spectacles,

f=P1=−1 m=−100 cm

Hence, the far point of the person is 100cm. He might have a normal near point of 25cm. When he uses the spectacles, the objects placed at infinity produce virtual images at 100 cm. He uses the ability of accommodation of the eye-lens to see the objects placed 100 cm and 25 cm.

During old age, the person uses reading glasses of power, P=+2 D

The ability of accommodation is lost in old age. This defect is called presbyopia. As a result, he is unable to see clearly the objects placed at 25 cm.

Explanation:

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