Thanks in advance 1.) A farsighted person has a near point that is 48.0 cm from

Question

Thanks in advance

1.) A farsighted person has a near point that is 48.0 cm from her eyes. She wears eyeglasses that are designed to enable her to read a newspaper held at a distance of 27.0 cm from her eyes. Find the focal length of the eyeglasses, assuming each of the following.

(a) that they are worn 2.0 cm from the eyes
__________cm

(b) that they are worn 3.0 cm from the eyes
___________cm

2.) A nearsighted patient's far point is 0.627 m from her eyes. She is able to see distant objects in focus when wearing glasses with a refractive power of -1.65 diopters. What is the distance between her eyes and the glasses?
______________m

Explanation / Answer

here,

let the focal length of glasses be f

(a)

when they are worn 2 cm from the eyes

object distance , u = 27 - 2

u = 25 cm

image distance , v = 48 - 2

v = 46 cm

1/f = 1/u + 1/v

1/f = 1/25 + 1/46

f = 16.2 cm

the focal length of the eyeglasses is 16.2 cm

(b)

when they are worn 3 cm from the eyes

object distance , u = 27 - 3

u = 24 cm

image distance , v = 48 - 3

v = 45 cm

1/f = 1/u + 1/v

1/f = 1/24 + 1/45

f = 15.65 cm

the focal length of the eyeglasses is 15.65 cm

please ask seprate question in seprate posts

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