People who do very detailed work close up, such as jewellers, often can see obje

Question

People who do very detailed work close up, such as jewellers, often can see objects clearly at much closer distance than the normal 25 cm. What is the power of the eyes of a woman who can see an object clearly at a distance of only 9.00 cm? Assume that the distance from the cornea to the retina is 2.0 cm. (You do not need to enter any units.)
D

What is the size of an image of a 0.90 mm object, such as lettering inside a ring, held at this distance?

What would the size of the image be if the object were held at the normal 25 cm distance?

Explanation / Answer

Here ,

for the power of lens ,

do = 9 cm

di = 2 cm

Using lens formula

1/f = 1/9 + 1/2

f = 1.64 cm

Now, power = 100/f

Power = 100/1.64

Power = 61.11 D

the power of the lens is 61.11 D

B)

Now , the size of image , hi =- 2*0.90/9

hi =- 0.2 mm

the height of image is -0.2 mm

C)

for do = 25 cm

hi = -2 * 0.9/25

hi = -0.072 mm

the height of image is -0.072 mm

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