a myopic person has been using his spectacles of power minus 1 d for clear vision during his old age he also needs to use separate reading glasses of power plus 2.0 d explain what we have happened to his eyesight also calculate his near point
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The power of the spectacles used by the myopic person, P = −1.0 D
Focal length of the spectacles, f = 1/P = 1/-1x10-2= -100 cm
Hence, the far point of the person is 100 cm. He might have a normal near point of 25 cm. 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 between 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.
Focal length of the spectacles, f = 1/P = 1/-1x10-2= -100 cm
Hence, the far point of the person is 100 cm. He might have a normal near point of 25 cm. 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 between 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.
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